Flat Tow Wrangler YJ (Informational - Long)
02-06-2007, 01:04 PM
#1
Guest
Posts: n/a
Flat Tow Wrangler YJ (Informational - Long)
I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
five speed manual transmission. I assume it has the standard NP-231
transfer case.
Although I have successfully flat-towed my YJ (maximum of about 400
miles one-way and then return about a week later), I've recently
learned that the NP-231 (at least of this era) does not have a "true"
neutral position. Instead, while it does uncouple the transmission
from the transfer case, it also couples the front and rear outputs
together. If the front axle is engaged this causes gear backlash with
the potential to destroy the transfer case. If the Center Axle
Disconnect (CAD) on the front axle is disconnected (disengaged?), then
the backlash is eliminated.
The problem is that the vacuum operated CAD stays in the last position
it was put in. If you are preparing your YJ for flat towing and you
start the engine, the moment you shift the transfer case from 2WD to
Neutral the vacuum CAD engages the front axle. There you are with the
outputs of the transfer case locked together and the front axle live
instead of free-wheeling. Leaving you with the potential of blowing up
the transfer case.
The standard way to disengage the CAD under normal conditions (i.e.
you've been in 4WD and are now ready to resume normal 2WD operation)
is to place the transfer case into 2WD and then put the transmission
into reverse and back up several feet. This puts the front axle back
into free-wheeling mode (assuming everything is working properly), and
you can put the transmission into normal gear and drive off.
If you know the CAD is in this state then you can prepare for towing
simply by putting the transfer case into neutral without starting the
engine (no vacuum). Go ahead and put the transmission into neutral,
hook up to your tow vehicle and go. Some people recommend that you
leave the transmission in gear while towing. Since you have
disconnected the transmission when you put the transfer case in
neutral, this should not be necessary. Further, if the transmission is
in gear and the transfer case is accidently engaged (by a severe bump
maybe?) there will be bad consequences. You don't have to worry about
the transfer case lubrication because the rear output (which is
engaged) also drives the internal oil pump. As long as the CAD is
disengaged you are ready to tow.
Apparently when I've towed my YJ I been fortunate in that a)I
typically back in to park, therefore I've left the jeep with the CAD
disengaged and b)I normally don't have any reason to start the jeep
prior to putting the transfer case into neutral before hooking it up
to be towed. Since I didn't understand what I was doing, I could very
easily have destroyed my transfer case without knowing why.
Although I am comfortable with this, knowing how things work, there
are alternatives I discovered as I researched this issue.
1)Assuming that the CAD is already disengaged, you can just disconnect
the vacuum line from the CAD box. You'd be fine to start your engine
and move the jeep to the towing vehicle, hook up, put the transfer
case and transmission in neutral and go.
2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
you control the front axle lock by cable, you should know the state it
is in.
3)Install and use external locking hubs. Not pleasant to use in foul
weather, but again you always know the state of the front axle because
you set it.
4)Install a transfer case conversion that gives you a true neutral.
You'd never have to worry about the state of the front axle when you
put the transfer case into neutral then.
5)Finally, of course, you can always tow your jeep on a trailer.
Comments and questions are welcome.
Your mileage may vary.
Vehicles in mirror are closer than they appear.
Cheers, Ed Humphries
Atlanta, Georgia
five speed manual transmission. I assume it has the standard NP-231
transfer case.
Although I have successfully flat-towed my YJ (maximum of about 400
miles one-way and then return about a week later), I've recently
learned that the NP-231 (at least of this era) does not have a "true"
neutral position. Instead, while it does uncouple the transmission
from the transfer case, it also couples the front and rear outputs
together. If the front axle is engaged this causes gear backlash with
the potential to destroy the transfer case. If the Center Axle
Disconnect (CAD) on the front axle is disconnected (disengaged?), then
the backlash is eliminated.
The problem is that the vacuum operated CAD stays in the last position
it was put in. If you are preparing your YJ for flat towing and you
start the engine, the moment you shift the transfer case from 2WD to
Neutral the vacuum CAD engages the front axle. There you are with the
outputs of the transfer case locked together and the front axle live
instead of free-wheeling. Leaving you with the potential of blowing up
the transfer case.
The standard way to disengage the CAD under normal conditions (i.e.
you've been in 4WD and are now ready to resume normal 2WD operation)
is to place the transfer case into 2WD and then put the transmission
into reverse and back up several feet. This puts the front axle back
into free-wheeling mode (assuming everything is working properly), and
you can put the transmission into normal gear and drive off.
If you know the CAD is in this state then you can prepare for towing
simply by putting the transfer case into neutral without starting the
engine (no vacuum). Go ahead and put the transmission into neutral,
hook up to your tow vehicle and go. Some people recommend that you
leave the transmission in gear while towing. Since you have
disconnected the transmission when you put the transfer case in
neutral, this should not be necessary. Further, if the transmission is
in gear and the transfer case is accidently engaged (by a severe bump
maybe?) there will be bad consequences. You don't have to worry about
the transfer case lubrication because the rear output (which is
engaged) also drives the internal oil pump. As long as the CAD is
disengaged you are ready to tow.
Apparently when I've towed my YJ I been fortunate in that a)I
typically back in to park, therefore I've left the jeep with the CAD
disengaged and b)I normally don't have any reason to start the jeep
prior to putting the transfer case into neutral before hooking it up
to be towed. Since I didn't understand what I was doing, I could very
easily have destroyed my transfer case without knowing why.
Although I am comfortable with this, knowing how things work, there
are alternatives I discovered as I researched this issue.
1)Assuming that the CAD is already disengaged, you can just disconnect
the vacuum line from the CAD box. You'd be fine to start your engine
and move the jeep to the towing vehicle, hook up, put the transfer
case and transmission in neutral and go.
2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
you control the front axle lock by cable, you should know the state it
is in.
3)Install and use external locking hubs. Not pleasant to use in foul
weather, but again you always know the state of the front axle because
you set it.
4)Install a transfer case conversion that gives you a true neutral.
You'd never have to worry about the state of the front axle when you
put the transfer case into neutral then.
5)Finally, of course, you can always tow your jeep on a trailer.
Comments and questions are welcome.
Your mileage may vary.
Vehicles in mirror are closer than they appear.
Cheers, Ed Humphries
Atlanta, Georgia
02-06-2007, 02:08 PM
#2
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
On Feb 6, 12:04 pm, edh3...@bellsouth.net wrote:
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
02-06-2007, 02:08 PM
#3
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
On Feb 6, 12:04 pm, edh3...@bellsouth.net wrote:
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
02-06-2007, 02:08 PM
#4
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
On Feb 6, 12:04 pm, edh3...@bellsouth.net wrote:
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
02-06-2007, 02:08 PM
#5
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
On Feb 6, 12:04 pm, edh3...@bellsouth.net wrote:
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
This is good to know. Thanks for posting.
Could option 4 cause problems? It seems that a true neutral might
leave the internal oil pump disconnected.
02-06-2007, 03:49 PM
#6
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
Where do you get this information? I suspect that some or all of it is
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
02-06-2007, 03:49 PM
#7
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
Where do you get this information? I suspect that some or all of it is
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
02-06-2007, 03:49 PM
#8
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
Where do you get this information? I suspect that some or all of it is
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
02-06-2007, 03:49 PM
#9
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
Where do you get this information? I suspect that some or all of it is
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
false. I can't believe that neutral would lock the axles together, but then
again we are dealing with a crappy second rate American manufacturer (this
bit is for Stupendous Man).
I have always put the transfer case in neutral, transmission in gear, engine
running and let out the clutch before flat towing. This lets me know that
the transfer case is really disconnected. Then I shut off the engine,
leaving the transmission in gear, and have towed several thousand miles in
this fashion. I am sure that the center axle disconnect has indeed been
disconnected every time, and that the transfer case has been in neutral,
because I never noticed any binding, jerking, suspicious noises, difficulty
steering or transfer case damage. Next time I do this, it won't hurt to
reach underneath and verify that the front drive shaft turns freely of
course.
If you leave the transmission in neutral, it can be driven by a transfer
case in neutral because of friction and oil viscosity. This can lead to a
dry bearing condition and transmission mainshaft damage. Always have the
transmission in gear or park when flat towing.
Earle
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
> I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
02-06-2007, 04:42 PM
#10
Guest
Posts: n/a
Re: Flat Tow Wrangler YJ (Informational - Long)
You read that in the 4 Wheel Parts mag, eh?
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
>I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
<edh3007@bellsouth.net> wrote in message
news:1170785062.593064.102050@v33g2000cwv.googlegr oups.com...
>I have a 1991 Jeep Wrangler YJ with the 2.5L four-cylinder and stock
> five speed manual transmission. I assume it has the standard NP-231
> transfer case.
>
> Although I have successfully flat-towed my YJ (maximum of about 400
> miles one-way and then return about a week later), I've recently
> learned that the NP-231 (at least of this era) does not have a "true"
> neutral position. Instead, while it does uncouple the transmission
> from the transfer case, it also couples the front and rear outputs
> together. If the front axle is engaged this causes gear backlash with
> the potential to destroy the transfer case. If the Center Axle
> Disconnect (CAD) on the front axle is disconnected (disengaged?), then
> the backlash is eliminated.
>
> The problem is that the vacuum operated CAD stays in the last position
> it was put in. If you are preparing your YJ for flat towing and you
> start the engine, the moment you shift the transfer case from 2WD to
> Neutral the vacuum CAD engages the front axle. There you are with the
> outputs of the transfer case locked together and the front axle live
> instead of free-wheeling. Leaving you with the potential of blowing up
> the transfer case.
>
> The standard way to disengage the CAD under normal conditions (i.e.
> you've been in 4WD and are now ready to resume normal 2WD operation)
> is to place the transfer case into 2WD and then put the transmission
> into reverse and back up several feet. This puts the front axle back
> into free-wheeling mode (assuming everything is working properly), and
> you can put the transmission into normal gear and drive off.
>
> If you know the CAD is in this state then you can prepare for towing
> simply by putting the transfer case into neutral without starting the
> engine (no vacuum). Go ahead and put the transmission into neutral,
> hook up to your tow vehicle and go. Some people recommend that you
> leave the transmission in gear while towing. Since you have
> disconnected the transmission when you put the transfer case in
> neutral, this should not be necessary. Further, if the transmission is
> in gear and the transfer case is accidently engaged (by a severe bump
> maybe?) there will be bad consequences. You don't have to worry about
> the transfer case lubrication because the rear output (which is
> engaged) also drives the internal oil pump. As long as the CAD is
> disengaged you are ready to tow.
>
> Apparently when I've towed my YJ I been fortunate in that a)I
> typically back in to park, therefore I've left the jeep with the CAD
> disengaged and b)I normally don't have any reason to start the jeep
> prior to putting the transfer case into neutral before hooking it up
> to be towed. Since I didn't understand what I was doing, I could very
> easily have destroyed my transfer case without knowing why.
>
> Although I am comfortable with this, knowing how things work, there
> are alternatives I discovered as I researched this issue.
>
> 1)Assuming that the CAD is already disengaged, you can just disconnect
> the vacuum line from the CAD box. You'd be fine to start your engine
> and move the jeep to the towing vehicle, hook up, put the transfer
> case and transmission in neutral and go.
>
> 2)Install and use a Posi-Lock device instead of the vacuum CAD. Since
> you control the front axle lock by cable, you should know the state it
> is in.
>
> 3)Install and use external locking hubs. Not pleasant to use in foul
> weather, but again you always know the state of the front axle because
> you set it.
>
> 4)Install a transfer case conversion that gives you a true neutral.
> You'd never have to worry about the state of the front axle when you
> put the transfer case into neutral then.
>
> 5)Finally, of course, you can always tow your jeep on a trailer.
>
> Comments and questions are welcome.
>
> Your mileage may vary.
> Vehicles in mirror are closer than they appear.
> Cheers, Ed Humphries
> Atlanta, Georgia
>
