SnoMan

On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
<matt@nospamplease.com> wrote:

>Yes but in a solid axle vehicle caster is less critical than say in an IFS.


I am no so sure that I share this view. Solid axles as not immune to
this and in someways even more sensitive to it it you want it to track
correctly. My 89 4x4 burb will track for a long time hands off on a
good highway road before requiring correction even after 180K plus
miles. When it was new I added caster shims between spring pads and
springs to add about 2 degrees of positve caster to it or stock
setting as I recall because I did not like the way it tracked when new
and those shims are still in there today.
-----------------
TheSnoMan.com

Clay B Carley

SnoMan wrote:
> On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>
>>Yes but in a solid axle vehicle caster is less critical than say in an IFS.
>
>
>
> I am no so sure that I share this view. Solid axles as not immune to
> this and in someways even more sensitive to it it you want it to track
> correctly. My 89 4x4 burb will track for a long time hands off on a
> good highway road before requiring correction even after 180K plus
> miles. When it was new I added caster shims between spring pads and
> springs to add about 2 degrees of positve caster to it or stock
> setting as I recall because I did not like the way it tracked when new
> and those shims are still in there today.
> -----------------
> TheSnoMan.com

I think caster is important in any vehicle, no matter what front end
it's got. Caster helps, just like you say, essentially keeping the
wheel centered at high speeds. I would consider it a safety item even.
Incorrect caster can lead to an unstable vehicle on the highway.

If someone is going through the work to lift their vehicle enough to
turn the pinion up on the front end to the point of 0 caster or negative
caster, they should seriously consider having the axle either cut &
turned so that both pinion angle & caster are correct, or get a new axle
that's got the proper angles for your lift built in.

It might not be so much of an issue with ifs simply because the caster
can be set independantly of the pinion angle...

Clay

Clay B Carley

SnoMan wrote:
> On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>
>>Yes but in a solid axle vehicle caster is less critical than say in an IFS.
>
>
>
> I am no so sure that I share this view. Solid axles as not immune to
> this and in someways even more sensitive to it it you want it to track
> correctly. My 89 4x4 burb will track for a long time hands off on a
> good highway road before requiring correction even after 180K plus
> miles. When it was new I added caster shims between spring pads and
> springs to add about 2 degrees of positve caster to it or stock
> setting as I recall because I did not like the way it tracked when new
> and those shims are still in there today.
> -----------------
> TheSnoMan.com

I think caster is important in any vehicle, no matter what front end
it's got. Caster helps, just like you say, essentially keeping the
wheel centered at high speeds. I would consider it a safety item even.
Incorrect caster can lead to an unstable vehicle on the highway.

If someone is going through the work to lift their vehicle enough to
turn the pinion up on the front end to the point of 0 caster or negative
caster, they should seriously consider having the axle either cut &
turned so that both pinion angle & caster are correct, or get a new axle
that's got the proper angles for your lift built in.

It might not be so much of an issue with ifs simply because the caster
can be set independantly of the pinion angle...

Clay

Clay B Carley

SnoMan wrote:
> On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>
>>Yes but in a solid axle vehicle caster is less critical than say in an IFS.
>
>
>
> I am no so sure that I share this view. Solid axles as not immune to
> this and in someways even more sensitive to it it you want it to track
> correctly. My 89 4x4 burb will track for a long time hands off on a
> good highway road before requiring correction even after 180K plus
> miles. When it was new I added caster shims between spring pads and
> springs to add about 2 degrees of positve caster to it or stock
> setting as I recall because I did not like the way it tracked when new
> and those shims are still in there today.
> -----------------
> TheSnoMan.com

I think caster is important in any vehicle, no matter what front end
it's got. Caster helps, just like you say, essentially keeping the
wheel centered at high speeds. I would consider it a safety item even.
Incorrect caster can lead to an unstable vehicle on the highway.

If someone is going through the work to lift their vehicle enough to
turn the pinion up on the front end to the point of 0 caster or negative
caster, they should seriously consider having the axle either cut &
turned so that both pinion angle & caster are correct, or get a new axle
that's got the proper angles for your lift built in.

It might not be so much of an issue with ifs simply because the caster
can be set independantly of the pinion angle...

Clay

Clay B Carley

SnoMan wrote:
> On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
> <matt@nospamplease.com> wrote:
>
>
>>Yes but in a solid axle vehicle caster is less critical than say in an IFS.
>
>
>
> I am no so sure that I share this view. Solid axles as not immune to
> this and in someways even more sensitive to it it you want it to track
> correctly. My 89 4x4 burb will track for a long time hands off on a
> good highway road before requiring correction even after 180K plus
> miles. When it was new I added caster shims between spring pads and
> springs to add about 2 degrees of positve caster to it or stock
> setting as I recall because I did not like the way it tracked when new
> and those shims are still in there today.
> -----------------
> TheSnoMan.com

I think caster is important in any vehicle, no matter what front end
it's got. Caster helps, just like you say, essentially keeping the
wheel centered at high speeds. I would consider it a safety item even.
Incorrect caster can lead to an unstable vehicle on the highway.

If someone is going through the work to lift their vehicle enough to
turn the pinion up on the front end to the point of 0 caster or negative
caster, they should seriously consider having the axle either cut &
turned so that both pinion angle & caster are correct, or get a new axle
that's got the proper angles for your lift built in.

It might not be so much of an issue with ifs simply because the caster
can be set independantly of the pinion angle...

Clay

Matt Macchiarolo

"Paul Nelson" <paulnelsontx@gmail.com> wrote in message
news:C2BA35CD.67A23%paulnelsontx@gmail.com...
> The front driveshaft on my Rubicon is a CV shaft, with the double cardan
> joint just in front of the t-case. Isn't that the same for all TJs?
>

Yep, but pinion angle is measured at the pinion.

> The manual says the driveline angles are more important than the caster,
> but
> the specs appear to be for a single cardan front drive shaft instead of a
> double cardan.
> The specs are:
> Within 1 degree u-joint cancellation
> Operating angles less than 3 degrees
> At least half a degree operating angle.

I would surmise these are the specs for the rear driveshaft.

>
> Your t-case factory mount should give you 3 degrees down from horizontal.
> Factory front pinion angle is 3.2 degrees up from horizontal. This gives
> a
> u-joint cancellation of .2 degrees. The t-case output yoke operating
> angle
> is 1.9 degrees and the pinion input yoke operating angle is 1.7 degrees.
>
> You can increase the operating angle by about one degree at the t-case
> yoke.
> Any mathematicians know how much lift that is? I don't know the length of
> the front drive shaft, but I'd have to say not much. That's why you see a
> lot of t-case lowering kits.
>

The T case lowering kits are primarily to correct the rear driveshaft
angles, not front driveline angles.

> If the driveline angle is greater that three degrees, you will get a
> steady
> vibe in the pinion shaft which will eventually wear out the pinion
> bearing.
> If you have a single cardan joint in the drive shaft, you will get a
> similar
> vibe in the t-case output yoke. The vibe will be twice the rotational
> speed
> of the drive shaft because the pinion will actually speed up and slow down
> twice per revolution. At 2000 RPM, the vibe is like a hum (close to
> 60Hz),
> so it isn't that noticeable. At slower speeds, there is less force on the
> u-joint, and also hard to notice the vibe. You won't see the damage
> coming!
>
> If you have a double cardan joint in your front drive shaft, I think the
> specs in the repair manual are less critical. On my rubicon, the double
> cardan is up near the t-case yoke, so the critical angles will be down
> near
> the pinion. You want a small operating angle, probably half a degree. If
> the operating angle is zero, the u-joint at the pinion will not stay
> lubricated and may freeze up due to no rotation in the bearing caps.

You will probably see adequate rotation of the bearing caps from normal
cycling of the suspension during road operation.


> However, the operating angle at the double cardan can be larger than 3
> degrees.

True, but the pinion angle at the axle is what we're talking about.

Matt Macchiarolo

"Paul Nelson" <paulnelsontx@gmail.com> wrote in message
news:C2BA35CD.67A23%paulnelsontx@gmail.com...
> The front driveshaft on my Rubicon is a CV shaft, with the double cardan
> joint just in front of the t-case. Isn't that the same for all TJs?
>

Yep, but pinion angle is measured at the pinion.

> The manual says the driveline angles are more important than the caster,
> but
> the specs appear to be for a single cardan front drive shaft instead of a
> double cardan.
> The specs are:
> Within 1 degree u-joint cancellation
> Operating angles less than 3 degrees
> At least half a degree operating angle.

I would surmise these are the specs for the rear driveshaft.

>
> Your t-case factory mount should give you 3 degrees down from horizontal.
> Factory front pinion angle is 3.2 degrees up from horizontal. This gives
> a
> u-joint cancellation of .2 degrees. The t-case output yoke operating
> angle
> is 1.9 degrees and the pinion input yoke operating angle is 1.7 degrees.
>
> You can increase the operating angle by about one degree at the t-case
> yoke.
> Any mathematicians know how much lift that is? I don't know the length of
> the front drive shaft, but I'd have to say not much. That's why you see a
> lot of t-case lowering kits.
>

The T case lowering kits are primarily to correct the rear driveshaft
angles, not front driveline angles.

> If the driveline angle is greater that three degrees, you will get a
> steady
> vibe in the pinion shaft which will eventually wear out the pinion
> bearing.
> If you have a single cardan joint in the drive shaft, you will get a
> similar
> vibe in the t-case output yoke. The vibe will be twice the rotational
> speed
> of the drive shaft because the pinion will actually speed up and slow down
> twice per revolution. At 2000 RPM, the vibe is like a hum (close to
> 60Hz),
> so it isn't that noticeable. At slower speeds, there is less force on the
> u-joint, and also hard to notice the vibe. You won't see the damage
> coming!
>
> If you have a double cardan joint in your front drive shaft, I think the
> specs in the repair manual are less critical. On my rubicon, the double
> cardan is up near the t-case yoke, so the critical angles will be down
> near
> the pinion. You want a small operating angle, probably half a degree. If
> the operating angle is zero, the u-joint at the pinion will not stay
> lubricated and may freeze up due to no rotation in the bearing caps.

You will probably see adequate rotation of the bearing caps from normal
cycling of the suspension during road operation.


> However, the operating angle at the double cardan can be larger than 3
> degrees.

True, but the pinion angle at the axle is what we're talking about.

Matt Macchiarolo

"Paul Nelson" <paulnelsontx@gmail.com> wrote in message
news:C2BA35CD.67A23%paulnelsontx@gmail.com...
> The front driveshaft on my Rubicon is a CV shaft, with the double cardan
> joint just in front of the t-case. Isn't that the same for all TJs?
>

Yep, but pinion angle is measured at the pinion.

> The manual says the driveline angles are more important than the caster,
> but
> the specs appear to be for a single cardan front drive shaft instead of a
> double cardan.
> The specs are:
> Within 1 degree u-joint cancellation
> Operating angles less than 3 degrees
> At least half a degree operating angle.

I would surmise these are the specs for the rear driveshaft.

>
> Your t-case factory mount should give you 3 degrees down from horizontal.
> Factory front pinion angle is 3.2 degrees up from horizontal. This gives
> a
> u-joint cancellation of .2 degrees. The t-case output yoke operating
> angle
> is 1.9 degrees and the pinion input yoke operating angle is 1.7 degrees.
>
> You can increase the operating angle by about one degree at the t-case
> yoke.
> Any mathematicians know how much lift that is? I don't know the length of
> the front drive shaft, but I'd have to say not much. That's why you see a
> lot of t-case lowering kits.
>

The T case lowering kits are primarily to correct the rear driveshaft
angles, not front driveline angles.

> If the driveline angle is greater that three degrees, you will get a
> steady
> vibe in the pinion shaft which will eventually wear out the pinion
> bearing.
> If you have a single cardan joint in the drive shaft, you will get a
> similar
> vibe in the t-case output yoke. The vibe will be twice the rotational
> speed
> of the drive shaft because the pinion will actually speed up and slow down
> twice per revolution. At 2000 RPM, the vibe is like a hum (close to
> 60Hz),
> so it isn't that noticeable. At slower speeds, there is less force on the
> u-joint, and also hard to notice the vibe. You won't see the damage
> coming!
>
> If you have a double cardan joint in your front drive shaft, I think the
> specs in the repair manual are less critical. On my rubicon, the double
> cardan is up near the t-case yoke, so the critical angles will be down
> near
> the pinion. You want a small operating angle, probably half a degree. If
> the operating angle is zero, the u-joint at the pinion will not stay
> lubricated and may freeze up due to no rotation in the bearing caps.

You will probably see adequate rotation of the bearing caps from normal
cycling of the suspension during road operation.


> However, the operating angle at the double cardan can be larger than 3
> degrees.

True, but the pinion angle at the axle is what we're talking about.

Matt Macchiarolo

"Paul Nelson" <paulnelsontx@gmail.com> wrote in message
news:C2BA35CD.67A23%paulnelsontx@gmail.com...
> The front driveshaft on my Rubicon is a CV shaft, with the double cardan
> joint just in front of the t-case. Isn't that the same for all TJs?
>

Yep, but pinion angle is measured at the pinion.

> The manual says the driveline angles are more important than the caster,
> but
> the specs appear to be for a single cardan front drive shaft instead of a
> double cardan.
> The specs are:
> Within 1 degree u-joint cancellation
> Operating angles less than 3 degrees
> At least half a degree operating angle.

I would surmise these are the specs for the rear driveshaft.

>
> Your t-case factory mount should give you 3 degrees down from horizontal.
> Factory front pinion angle is 3.2 degrees up from horizontal. This gives
> a
> u-joint cancellation of .2 degrees. The t-case output yoke operating
> angle
> is 1.9 degrees and the pinion input yoke operating angle is 1.7 degrees.
>
> You can increase the operating angle by about one degree at the t-case
> yoke.
> Any mathematicians know how much lift that is? I don't know the length of
> the front drive shaft, but I'd have to say not much. That's why you see a
> lot of t-case lowering kits.
>

The T case lowering kits are primarily to correct the rear driveshaft
angles, not front driveline angles.

> If the driveline angle is greater that three degrees, you will get a
> steady
> vibe in the pinion shaft which will eventually wear out the pinion
> bearing.
> If you have a single cardan joint in the drive shaft, you will get a
> similar
> vibe in the t-case output yoke. The vibe will be twice the rotational
> speed
> of the drive shaft because the pinion will actually speed up and slow down
> twice per revolution. At 2000 RPM, the vibe is like a hum (close to
> 60Hz),
> so it isn't that noticeable. At slower speeds, there is less force on the
> u-joint, and also hard to notice the vibe. You won't see the damage
> coming!
>
> If you have a double cardan joint in your front drive shaft, I think the
> specs in the repair manual are less critical. On my rubicon, the double
> cardan is up near the t-case yoke, so the critical angles will be down
> near
> the pinion. You want a small operating angle, probably half a degree. If
> the operating angle is zero, the u-joint at the pinion will not stay
> lubricated and may freeze up due to no rotation in the bearing caps.

You will probably see adequate rotation of the bearing caps from normal
cycling of the suspension during road operation.


> However, the operating angle at the double cardan can be larger than 3
> degrees.

True, but the pinion angle at the axle is what we're talking about.

Matt Macchiarolo

"Clay B Carley" <cbc@corp.sonic.net> wrote in message
news:4694f601$0$14127$742ec2ed@news.sonic.net...
> SnoMan wrote:
>> On Wed, 11 Jul 2007 07:55:41 -0400, "Matt Macchiarolo"
>> <matt@nospamplease.com> wrote:
>>
>>
>>>Yes but in a solid axle vehicle caster is less critical than say in an
>>>IFS.
>>
>>
>>
>> I am no so sure that I share this view. Solid axles as not immune to
>> this and in someways even more sensitive to it it you want it to track
>> correctly. My 89 4x4 burb will track for a long time hands off on a
>> good highway road before requiring correction even after 180K plus
>> miles. When it was new I added caster shims between spring pads and
>> springs to add about 2 degrees of positve caster to it or stock
>> setting as I recall because I did not like the way it tracked when new
>> and those shims are still in there today. -----------------
>> TheSnoMan.com
>
> I think caster is important in any vehicle, no matter what front end it's
> got.

I agree, I never said it wasn't important, I said things like toe-in and
draglink settings are more critical. To clarify, that would be on a
moderately lifted Jeep like mine, where the caster was affected by the
pinion angle ajdjustment , yet it does track well on the highway.

Caster helps, just like you say, essentially keeping the
> wheel centered at high speeds. I would consider it a safety item even.
> Incorrect caster can lead to an unstable vehicle on the highway.
>
> If someone is going through the work to lift their vehicle enough to turn
> the pinion up on the front end to the point of 0 caster or negative
> caster, they should seriously consider having the axle either cut & turned
> so that both pinion angle & caster are correct, or get a new axle that's
> got the proper angles for your lift built in.

Agreed, but a typical 4-5" lift wouldn't set the caster so far out of spec
as to make the handling unsafe.

>
> It might not be so much of an issue with ifs simply because the caster can
> be set independantly of the pinion angle...
>
> Clay