On Wed, 13 Dec 2006 10:49:58 -0500, Mike Romain <romainm@sympatico.ca>
wrote:
>You are describing the noise and feel of a blown u-joint.
>
>If you block the wheels and put it in neutral to unload the drivetrain,
>you can go under and check the driveshaft u-joints. You twist and push
>at them as well as do a visual looking for rust stains around the caps.
>One arm on one will likely be just flopping around.

I'll get under it tonight and have a look... I'm kinda surprised it
would only do this when the thing has been sitting for a while,
though.

Wouldn't a damaged u-joint pretty consistently give you the same
"clunk", when shifting from park to reverse *or* drive? (this only
happens going into reverse from park, and only after it's been sitting
for a while).

The transmission always seems to shift a bit harsher when it's cooler
outside (than our standard 98 degree summer weather)... maybe this is
also temperature related, too...

Thanks for the tips -

Robert Giles

 

On Wed, 13 Dec 2006 10:49:58 -0500, Mike Romain <romainm@sympatico.ca>
wrote:
>You are describing the noise and feel of a blown u-joint.
>
>If you block the wheels and put it in neutral to unload the drivetrain,
>you can go under and check the driveshaft u-joints. You twist and push
>at them as well as do a visual looking for rust stains around the caps.
>One arm on one will likely be just flopping around.

I'll get under it tonight and have a look... I'm kinda surprised it
would only do this when the thing has been sitting for a while,
though.

Wouldn't a damaged u-joint pretty consistently give you the same
"clunk", when shifting from park to reverse *or* drive? (this only
happens going into reverse from park, and only after it's been sitting
for a while).

The transmission always seems to shift a bit harsher when it's cooler
outside (than our standard 98 degree summer weather)... maybe this is
also temperature related, too...

Thanks for the tips -

Robert Giles

 

On 13 Dec 2006 10:20:55 -0800, "Jon" <jongoddard@gmail.com> wrote:
>Your 42re doesn't circulate fluid through the torque converter when it
>is in park -- the logic from the factory was to minimize parasitic
>losses when the vehicle wasn't "in use". When the front pump bushing
>has worn a bit, you get converter "drainback" (whether or not you have
>a check valve in the cooler line). The transmission pump circulates
>through the converter and cooler when in any position but park -- so
>there's the one-second delay from extended shut-down. You're not
>gassing it during the delay, are you?

Nope - foot on the brake, waiting for the "clunk" to happen. This is
definitely a new thing - up until about two months ago, never got the
loud clunk or the delay when shifting.

The transmission has always acted strange during the fall/winter
months - since I've owned it (2001)... very harsh shifting and
abnormal shift points until warm, but I assumed this was the ECU
revving the engine higher (3K-4K RPM) to warm driveline components up
(but y'all are the experts - I'm just guessing here and have
absolutely zero experience with transmission problems).

>On top of it all, that transmission uses unregulated, full-pump
>pressure when in reverse. Hotter fluid -- therefore thinner and easier
>for the torque converter to move through -- would make for a softer
>engagement. I'm supposing that all these factors lead to the harsh
>reverse engagement -- and therefore the louder clunk than from another
>gear or a quick restart. So I'm with the others on bad u-joint/worn
>spiders/bad motor or transmission mount potentially making the audible
>clunk after a rougher than usual shift from park.

Ok - would a bad transmission mount be detectable just by looking at
it? (I haven't looked, but I'm guessing there's some kind of heavy
duty rubber grommets that may crack / degrade over time?)

>Take a walk over to alt.autos.dodge.trucks, there's a handful of guys
>(i.e. Tom Lawrence) who are very knowledgeable about this transmission.

Ok - thanks again for the help on this!

Robert Giles

 

On 13 Dec 2006 10:20:55 -0800, "Jon" <jongoddard@gmail.com> wrote:
>Your 42re doesn't circulate fluid through the torque converter when it
>is in park -- the logic from the factory was to minimize parasitic
>losses when the vehicle wasn't "in use". When the front pump bushing
>has worn a bit, you get converter "drainback" (whether or not you have
>a check valve in the cooler line). The transmission pump circulates
>through the converter and cooler when in any position but park -- so
>there's the one-second delay from extended shut-down. You're not
>gassing it during the delay, are you?

Nope - foot on the brake, waiting for the "clunk" to happen. This is
definitely a new thing - up until about two months ago, never got the
loud clunk or the delay when shifting.

The transmission has always acted strange during the fall/winter
months - since I've owned it (2001)... very harsh shifting and
abnormal shift points until warm, but I assumed this was the ECU
revving the engine higher (3K-4K RPM) to warm driveline components up
(but y'all are the experts - I'm just guessing here and have
absolutely zero experience with transmission problems).

>On top of it all, that transmission uses unregulated, full-pump
>pressure when in reverse. Hotter fluid -- therefore thinner and easier
>for the torque converter to move through -- would make for a softer
>engagement. I'm supposing that all these factors lead to the harsh
>reverse engagement -- and therefore the louder clunk than from another
>gear or a quick restart. So I'm with the others on bad u-joint/worn
>spiders/bad motor or transmission mount potentially making the audible
>clunk after a rougher than usual shift from park.

Ok - would a bad transmission mount be detectable just by looking at
it? (I haven't looked, but I'm guessing there's some kind of heavy
duty rubber grommets that may crack / degrade over time?)

>Take a walk over to alt.autos.dodge.trucks, there's a handful of guys
>(i.e. Tom Lawrence) who are very knowledgeable about this transmission.

Ok - thanks again for the help on this!

Robert Giles

 

On 13 Dec 2006 10:20:55 -0800, "Jon" <jongoddard@gmail.com> wrote:
>Your 42re doesn't circulate fluid through the torque converter when it
>is in park -- the logic from the factory was to minimize parasitic
>losses when the vehicle wasn't "in use". When the front pump bushing
>has worn a bit, you get converter "drainback" (whether or not you have
>a check valve in the cooler line). The transmission pump circulates
>through the converter and cooler when in any position but park -- so
>there's the one-second delay from extended shut-down. You're not
>gassing it during the delay, are you?

Nope - foot on the brake, waiting for the "clunk" to happen. This is
definitely a new thing - up until about two months ago, never got the
loud clunk or the delay when shifting.

The transmission has always acted strange during the fall/winter
months - since I've owned it (2001)... very harsh shifting and
abnormal shift points until warm, but I assumed this was the ECU
revving the engine higher (3K-4K RPM) to warm driveline components up
(but y'all are the experts - I'm just guessing here and have
absolutely zero experience with transmission problems).

>On top of it all, that transmission uses unregulated, full-pump
>pressure when in reverse. Hotter fluid -- therefore thinner and easier
>for the torque converter to move through -- would make for a softer
>engagement. I'm supposing that all these factors lead to the harsh
>reverse engagement -- and therefore the louder clunk than from another
>gear or a quick restart. So I'm with the others on bad u-joint/worn
>spiders/bad motor or transmission mount potentially making the audible
>clunk after a rougher than usual shift from park.

Ok - would a bad transmission mount be detectable just by looking at
it? (I haven't looked, but I'm guessing there's some kind of heavy
duty rubber grommets that may crack / degrade over time?)

>Take a walk over to alt.autos.dodge.trucks, there's a handful of guys
>(i.e. Tom Lawrence) who are very knowledgeable about this transmission.

Ok - thanks again for the help on this!

Robert Giles

 

On Wed, 13 Dec 2006 10:44:13 -0500, "billy ray"
<billy_ray@SPAMfuse.net> wrote:
>Your Factory Service Manual should have a whole transmission section with
>diagnosis charts.

Thanks for the URL - I'd skimmed through the 45RFE section in my book
(not realizing up until a few days ago that I had a 42RE) and missed
the condition / resolution part about "harsh engagement"...

Duh...

 

On Wed, 13 Dec 2006 10:44:13 -0500, "billy ray"
<billy_ray@SPAMfuse.net> wrote:
>Your Factory Service Manual should have a whole transmission section with
>diagnosis charts.

Thanks for the URL - I'd skimmed through the 45RFE section in my book
(not realizing up until a few days ago that I had a 42RE) and missed
the condition / resolution part about "harsh engagement"...

Duh...

 

On Wed, 13 Dec 2006 10:44:13 -0500, "billy ray"
<billy_ray@SPAMfuse.net> wrote:
>Your Factory Service Manual should have a whole transmission section with
>diagnosis charts.

Thanks for the URL - I'd skimmed through the 45RFE section in my book
(not realizing up until a few days ago that I had a 42RE) and missed
the condition / resolution part about "harsh engagement"...

Duh...

 

Robert,

So I think we have two separate issues, one has pointed out the other.

Transmission servicing will include dropping the pan for inspection,
adjustment to the bands, replacement of the filter, and in doing so
replacing roughly 1/2 the fluid in the transmission. If you think a
previous owner might have had it serviced with the wrong fluid in there
(every container of type 3/4 I've come across has NOT smelled
distinctly sweet like Dexron -- T 3/4 is rather foul, even mistaken as
burnt by those who haven't run across it) you might have to pop for a
"fluid exchange" service -- making sure the proper fluid is used. I
dunno, that might be overkill, but every source I've found talks at
length of the sensitivity of this transmission to the proper fluid
type. Since bands that are out of adjustment can give rise to your
symptoms, it's worth at least trying to establish a baseline -- you're
due for service either way.

U-Joints fail from wear, loss of lubrication, and component
breakage....or a combination. In the early stages, a dry joint, or one
that has just one set of bearings failing, might not make noise or get
shifted out of position by a smooth transition -- sometimes only by a
rough shift or higher load do they display a problem. As previuos
posters pointed out, a good physical and visual inspection usually does
the trick.

Your dipstick won't tell you much about contamination from wear -- the
pan accumulates a fair amount of material, and an educated eye can make
a judgement call based on amount and size of debris as to whether it's
normal for the use/mileage or if something is out of whack.

Yup -- an engine or transmission mount has the rubber isolation pieces
break down over time, leading to excessive movement (often exhaust
parts contact something they're not supposed to) or metal to metal
contact at the mount itself. At 6 years/70k, I don't think that's the
#1 source of a clunk, but try this:

Get someone to duplicate the noise for you, while you're down there
watching and listening -- out of the path of travel, please. That will
let you know what end of the vehicle is making the noise, and I bet
dollars to doughnuts you can I.D. the source from there.

Please post as you progress!

Jon



Robert Giles wrote:
> On 13 Dec 2006 10:20:55 -0800, "Jon" <jongoddard@gmail.com> wrote:
> >Your 42re doesn't circulate fluid through the torque converter when it
> >is in park -- the logic from the factory was to minimize parasitic
> >losses when the vehicle wasn't "in use". When the front pump bushing
> >has worn a bit, you get converter "drainback" (whether or not you have
> >a check valve in the cooler line). The transmission pump circulates
> >through the converter and cooler when in any position but park -- so
> >there's the one-second delay from extended shut-down. You're not
> >gassing it during the delay, are you?
>
> Nope - foot on the brake, waiting for the "clunk" to happen. This is
> definitely a new thing - up until about two months ago, never got the
> loud clunk or the delay when shifting.
>
> The transmission has always acted strange during the fall/winter
> months - since I've owned it (2001)... very harsh shifting and
> abnormal shift points until warm, but I assumed this was the ECU
> revving the engine higher (3K-4K RPM) to warm driveline components up
> (but y'all are the experts - I'm just guessing here and have
> absolutely zero experience with transmission problems).
>
> >On top of it all, that transmission uses unregulated, full-pump
> >pressure when in reverse. Hotter fluid -- therefore thinner and easier
> >for the torque converter to move through -- would make for a softer
> >engagement. I'm supposing that all these factors lead to the harsh
> >reverse engagement -- and therefore the louder clunk than from another
> >gear or a quick restart. So I'm with the others on bad u-joint/worn
> >spiders/bad motor or transmission mount potentially making the audible
> >clunk after a rougher than usual shift from park.
>
> Ok - would a bad transmission mount be detectable just by looking at
> it? (I haven't looked, but I'm guessing there's some kind of heavy
> duty rubber grommets that may crack / degrade over time?)
>
> >Take a walk over to alt.autos.dodge.trucks, there's a handful of guys
> >(i.e. Tom Lawrence) who are very knowledgeable about this transmission.
>
> Ok - thanks again for the help on this!
>
> Robert Giles

 

Robert,

So I think we have two separate issues, one has pointed out the other.

Transmission servicing will include dropping the pan for inspection,
adjustment to the bands, replacement of the filter, and in doing so
replacing roughly 1/2 the fluid in the transmission. If you think a
previous owner might have had it serviced with the wrong fluid in there
(every container of type 3/4 I've come across has NOT smelled
distinctly sweet like Dexron -- T 3/4 is rather foul, even mistaken as
burnt by those who haven't run across it) you might have to pop for a
"fluid exchange" service -- making sure the proper fluid is used. I
dunno, that might be overkill, but every source I've found talks at
length of the sensitivity of this transmission to the proper fluid
type. Since bands that are out of adjustment can give rise to your
symptoms, it's worth at least trying to establish a baseline -- you're
due for service either way.

U-Joints fail from wear, loss of lubrication, and component
breakage....or a combination. In the early stages, a dry joint, or one
that has just one set of bearings failing, might not make noise or get
shifted out of position by a smooth transition -- sometimes only by a
rough shift or higher load do they display a problem. As previuos
posters pointed out, a good physical and visual inspection usually does
the trick.

Your dipstick won't tell you much about contamination from wear -- the
pan accumulates a fair amount of material, and an educated eye can make
a judgement call based on amount and size of debris as to whether it's
normal for the use/mileage or if something is out of whack.

Yup -- an engine or transmission mount has the rubber isolation pieces
break down over time, leading to excessive movement (often exhaust
parts contact something they're not supposed to) or metal to metal
contact at the mount itself. At 6 years/70k, I don't think that's the
#1 source of a clunk, but try this:

Get someone to duplicate the noise for you, while you're down there
watching and listening -- out of the path of travel, please. That will
let you know what end of the vehicle is making the noise, and I bet
dollars to doughnuts you can I.D. the source from there.

Please post as you progress!

Jon



Robert Giles wrote:
> On 13 Dec 2006 10:20:55 -0800, "Jon" <jongoddard@gmail.com> wrote:
> >Your 42re doesn't circulate fluid through the torque converter when it
> >is in park -- the logic from the factory was to minimize parasitic
> >losses when the vehicle wasn't "in use". When the front pump bushing
> >has worn a bit, you get converter "drainback" (whether or not you have
> >a check valve in the cooler line). The transmission pump circulates
> >through the converter and cooler when in any position but park -- so
> >there's the one-second delay from extended shut-down. You're not
> >gassing it during the delay, are you?
>
> Nope - foot on the brake, waiting for the "clunk" to happen. This is
> definitely a new thing - up until about two months ago, never got the
> loud clunk or the delay when shifting.
>
> The transmission has always acted strange during the fall/winter
> months - since I've owned it (2001)... very harsh shifting and
> abnormal shift points until warm, but I assumed this was the ECU
> revving the engine higher (3K-4K RPM) to warm driveline components up
> (but y'all are the experts - I'm just guessing here and have
> absolutely zero experience with transmission problems).
>
> >On top of it all, that transmission uses unregulated, full-pump
> >pressure when in reverse. Hotter fluid -- therefore thinner and easier
> >for the torque converter to move through -- would make for a softer
> >engagement. I'm supposing that all these factors lead to the harsh
> >reverse engagement -- and therefore the louder clunk than from another
> >gear or a quick restart. So I'm with the others on bad u-joint/worn
> >spiders/bad motor or transmission mount potentially making the audible
> >clunk after a rougher than usual shift from park.
>
> Ok - would a bad transmission mount be detectable just by looking at
> it? (I haven't looked, but I'm guessing there's some kind of heavy
> duty rubber grommets that may crack / degrade over time?)
>
> >Take a walk over to alt.autos.dodge.trucks, there's a handful of guys
> >(i.e. Tom Lawrence) who are very knowledgeable about this transmission.
>
> Ok - thanks again for the help on this!
>
> Robert Giles