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  #16  
Old April 3rd, 2018, 13:51
Rockwood Rockwood is offline
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Re: Clunk/lurch into Drive, but not Reverse

Check for up/down/left/right play on the pinion yoke.

Otherwise, it's fairly normal. Mine clunks.
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  #17  
Old June 10th, 2018, 12:35
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

FOLLOW UP: Just got my XJ back from the transmission shop. It was in there for over 2 months, during which he completely rebuilt the transmission and the torque converter, replaced the valve body and the transmission control module and even the transmission case, and at the end he said that he and all of his fellow transmission shop owners on a network were all completely stumped as to why none of that fixed the problem. He did not charge me for any of this, because he said that he does not charge if he can't fix the problem. He was still pretty much 100% sure that the transmission would be the problem, but at that point he said the only thing that I could do would be to actually replace the entire transmission with a rebuilt one, and hope that doing that would solve the problem.

So... It seems that one of these things has to be true:

1.) All of these Transmission Specialists plus a certified Jeep Master Mechanic are all completely wrong, and the problem is not related to the transmission at all, and my transmission mechanic invested over 2 months of time plus the parts and labor required to rebuild the transmission and torque converter etc. based upon a wrong assumption that the transmission was the problem.

OR

2.) Somehow my transmission has such a rare and freakish problem that it was able to avoid being fixed despite the transmission almost being completely replaced.

I'll just have to keep searching the internet to try to find someone else who has experienced this obviously very rare problem.
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  #18  
Old October 29th, 2018, 15:42
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Is the clunk/lurch when put into gear caused by a sticking slip yoke ever unidirectional? I found this video where GRAVITY was causing a unidirectional clunk/lurch. If gravity could cause the slip yoke to slide down the shaft when in Neutral, removing play unidirectionally, then it could cause a unidirectional clunk/lurch:

https://www.youtube.com/watch?v=DelqMr6Mmaw

GRAVITY only works in one direction, and if part of the drive train stucture has up and down play in it, that would explain how the clunk/lurch could be unidirectional, because gravity can serve to remove play unidirectionally when in Neutral gear. His differential support bracket was being lifted up when in Drive, then it would fall back down to normal position when in Neutral, leaving no play to cause a clunk/lurch when put into Reverse.

I guess the first easy step to take would be to park the XJ on a very steep hill in all possible orientations, and see if the clunk/lurch changes in any position. But if the part that is shifting up and down is actually shifting nearly perpendicular to the ground, then I'd have to suspend the XJ upside down to learn anything. If so, then I'll just have to mount a camera at various points in the drive train to see what is shifting up and down when I shift from Neutral to Drive and back.
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  #19  
Old October 29th, 2018, 15:58
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Come to think of it...does the slip yoke even slip enough to cause a clunk/lurch when the XJ is sitting still?
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  #20  
Old October 30th, 2018, 11:59
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Re: Clunk/lurch into Drive, but not Reverse

Have you actually been under the Jeep when someone is shifting to see where the noise is coming from? If it that loud and that noticeable, you will have no trouble ascertaining what is making the noise.

As far as the slip yoke "sliding down" due to gravity. It cannot happen! The rear driveshaft is a single piece with end one fastened to the axle differential pinion, the other end slides on the slip yoke at the transfer case. The only time the slip yoke "slides" is when the axle cycles up and down, changing the distance between the axle and the transfer case.

So, get under it and listen/feel and report back.
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  #21  
Old October 30th, 2018, 14:35
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Re: Clunk/lurch into Drive, but not Reverse

Your transmission guy must not be a differential guy, 'cause that is where the clunk is coming from.
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  #22  
Old October 30th, 2018, 14:59
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Re: Clunk/lurch into Drive, but not Reverse

Have you pulled the rear driveshaft and lubed the slip yoke at all? When the slip yokes get dry it can cause a clunking on acceleration, which might be what you're seeing when you put it in drive.
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  #23  
Old October 30th, 2018, 22:38
lawsoncl lawsoncl is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by soyjer View Post
FOLLOW UP: Just got my XJ back from the transmission shop. It was in there for over 2 months, during which he completely rebuilt the transmission and the torque converter, replaced the valve body and the transmission control module and even the transmission case, and at the end he said that he and all of his fellow transmission shop owners on a network were all completely stumped as to why none of that fixed the problem. He did not charge me for any of this, because he said that he does not charge if he can't fix the problem. He was still pretty much 100% sure that the transmission would be the problem, but at that point he said the only thing that I could do would be to actually replace the entire transmission with a rebuilt one, and hope that doing that would solve the problem.

Wow, he did a lot of unnecessary work! Even replaced the TCM, he really thought it was an electronic issue? Can't fault him though, since he was incredibly honest and he didn't charge you for what would have been a very expensive bill at any other place even if they didn't fix the issue. The AW4 is pretty robust and probably didn't need a rebuild, btw
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  #24  
Old October 31st, 2018, 08:06
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by Flyfisher View Post
Have you actually been under the Jeep when someone is shifting to see where the noise is coming from? If it that loud and that noticeable, you will have no trouble ascertaining what is making the noise.

As far as the slip yoke "sliding down" due to gravity. It cannot happen! The rear driveshaft is a single piece with end one fastened to the axle differential pinion, the other end slides on the slip yoke at the transfer case. The only time the slip yoke "slides" is when the axle cycles up and down, changing the distance between the axle and the transfer case.

So, get under it and listen/feel and report back.
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  #25  
Old October 31st, 2018, 16:04
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by Flyfisher View Post
Have you actually been under the Jeep when someone is shifting to see where the noise is coming from? If it that loud and that noticeable, you will have no trouble ascertaining what is making the noise.
Mechanics have forever run vehicles in place, either held in place with blocks, up on jack stands or on a lift, so the problem or noise can be isolated.
Surprised this wasn't done at the transmission shop or, if they did, the location of the noise could not be determined.

Block all four wheels, front and back, and have a helper shift it back in forth, from Drive to Reverse, while you observe what is going on underneath, looking in from both the driver and passenger sides.
With bigger tires, I like 4X4 blocks.
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  #26  
Old October 31st, 2018, 17:09
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

OK... I took the XJ out to a wide boat ramp and tried every possible XJ orientation and ways to shift into Drive including in 4H and 4L, and the only thing that that will eliminate the violent clunk/lurch completely is if the XJ is traveling either in 2H or 4H at > 10 mph when shifted into Drive, or at > 5mph if in 4L.

I got under the XJ (again) while it was being shifted, and the ringy sounding "clunk" noise comes from the differential, and I noticed that the degrees of travel of the rear drive shaft when shifting into Drive is more than twice the travel as when it is being shifted into Reverse (all U-joints are tight, btw). So far I've been trusting that the veteran Master Jeep Mechanic (who has worked on hundreds of XJ's) and the veteran transmission guy (who rebuilt the transmission for free) knew what they were talking about when they said that it is the transmission that is the problem and not the differential, but now I'm starting to wonder if it might be the differential that is the problem.

The assumption up until now has been that the transmission is causing the violent engagement clunk/lurch, but maybe it is just that the forward direction function of the differential has SO MUCH PLAY in it that the drive shaft has enough free play to be able to build up speed before the play is taken up, and what I am experiencing is the HAMMERING of the gears against one another when the play runs out. (If you hit a bell with a hammer from 6" away, it will ring loudly, but if you hit it from 1/2" away, it won't).

If it IS the differential, I don't know why this Chrysler 8.25 would be in such bad shape after only 98K miles, with none off-road. My understanding is that if the previous owner operated the 231 transfer case in 4wd on dry pavement, it would never hurt the rear differential, because the rear differential doesn't even know whether the XJ is in 2wd or 4wd, correct?

Another theory I had about this problem was that maybe the transmission is starting out in a high gear instead of low gear when placed into Drive, but that theory got shot down when I affirmed that it only goes into 1st gear when it is put into Drive. Shifting directly from Neutral to 1st gear with the gear selector gets rid of the clunk NOISE (which I think is the differential "ring" gear actually "ringing", but the lurch is pretty much just as violent as when going from Neutral to Drive.
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  #27  
Old October 31st, 2018, 17:25
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by Tim_MN View Post
Your transmission guy must not be a differential guy, 'cause that is where the clunk is coming from.
I'm starting to think that you are correct (see my full post down below if you want details). Questions about Chrysler 8.25:

1. Should the rotational play of the drive shaft be about the same when shifting into Drive vs. into Reverse? Mine has more than twice as much play in the Neutral to Drive direction.

2. Ever heard of a Chrysler 8.25 failing like that with 98K miles, none off-road, on a very well cared-for XJ?
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  #28  
Old October 31st, 2018, 17:38
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Just to add to the confusion (on my part, anyway), I just confirmed that despite the large difference in differential play when going into Drive vs. Reverse, if I MANUALLY rotate the drive shaft back and forth rotationally (U-Joints are tight, btw), the differential play is seems very minor to me:

With transmission and transfer case both in neutral, I'm measuring 4.5 degrees of play on the rear drive shaft (2.5 mm or .1", measured at outer surface of drive shaft).

(2.5mm play / 200mm circumstance) x 360 degrees = 4.5 degrees of play.
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  #29  
Old November 1st, 2018, 04:00
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Re: Clunk/lurch into Drive, but not Reverse

Since the differential spends 99.99 % of its life in forward drive, one might expect more wear on the forward motion side of the differential internals. The cause of any measurable excess wear is a good question. A teenaged male doing neutral drop burn outs would be a good suspect.

Chrysler Clunk is a commonly heard description of the symptoms. Have an experienced differential technician check/measure the ring and pinion backlash, the condition of the spider gears, the condition of and pre-load on the differential bearings, and the ring/pinion engagement pattern.
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Quote:
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Tim MAY be 100% correct, but why would a person automatically pick him as the expert .....

Last edited by Tim_MN; November 1st, 2018 at 04:03.
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  #30  
Old November 1st, 2018, 13:35
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Rob Mayercik Rob Mayercik is offline
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Re: Clunk/lurch into Drive, but not Reverse

98K doesn't seem like much - I'm still on the original 27-spline version of that with my '92 and it's got 256K miles on it with no issues.

Could whatever holds the pinion into the diff housing be loose (crush sleeve? yoke nut?), causing something that normally shouldn't rotate to have to spin a little before you start taking up the R&P mesh slack?

In other words, is the amount the rear driveshaft twists when you put it into Drive and it clunks equal to or greater than the amount you can twist it by hand? If putting it into drive gets more rotation, perhaps there really is something "else" rotating under the greater torque of the engine/trans that shouldn't be?
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