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  #46  
Old May 27th, 2019, 04:30
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TRCM TRCM is offline
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Re: Clunk/lurch into Drive, but not Reverse

Wow....my rear axle has about 5 times as much rotational movement, but never noticed the jerking around part......~175k on it.
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  #47  
Old May 27th, 2019, 07:40
dsbhealer dsbhealer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Holes in the flexplate can be checked by removing the inspection plate in the bell housing of the auto tranny. The oxygen sensor will block removal of one bolt holding the plate. Check for loose bolts. Do not overtighten the bolts or you will probably crack the flexplate. If you have had your torque converter replaced, then it is very unlikely that the shop would have missed enlarged holes in the flexplate.



A stretched chain in the transfer case is possible, but it would probably make noise when driving in 4 wheel drive. Play anywhere in the entire drivetrain could allow the system to accumulate the momentum to form an impulse (clunk) when the play is used up and the engine's rotation is finally delivered to the wheels or brakes. The more play, the higher the engine speed and the greater the stored energy (as in an engine raised up on a loose engine mount) the greater the clunk.


The engine is secured by the engine mounts against rotation. A loose mount allows the engine to lift on one side when the engine is put into gear or revved while driving. This can cause or contribute to a clunk. Loose flexplate bolts that allow rotation between the engine and torque converter can contribute to or cause the clunk. The longer this occurs, the more enlarged the holes become and the more pronounced this contribution to the clunk becomes. If there is play between the torque converter and the transmission shaft, that can contribute to the problem. If your torque converter is new, hopefully that is not an issue. Low transmission fluid or a worn transmission could contribute, but you have had that rebuilt, so hopefully that is not the issue. Binding in the slip yoke might contribute, it should be greased. Loose u-joints in the drive shaft can contribute. Increased backlash in the rear axle from improper adjustment, wear or a failing part inside the axle could contribute. Weak leaf springs or worn leaf spring bushings could allow play or wrapup contributing to the problem, but you would see some rotation of the axle housing, which I didn't notice in the video.



Several people mentioned checking the engine mounts. There are supports bolted to the engine block that can have loose or broken bolts and then there are the mounts which consist of rubber cushions (which wear out) and a metal strap around the rubber and fused to it (when new) and the bolts that hold it in place. Check all bolts for the supports and mounts. Watch the mounts when someone puts the vehicle from park to drive with the wheels blocked and the brake applied. See if the engine moves and if there is motion in the components of the mount or mount supports.


One mount looser than the other will explain the clunk being worse in park to drive vs park to reverse. The problem occurring more in 4x4 low from park to reverse is probably due to the increase torque in 4x4 low from the lower gear ratio. The 4x4 high or 2wd high has less torque to stress the drivetrain. Park to drive stresses one engine mount and support. Park to reverse stresses the other mount. If replacing engine mounts, replace both and the tranny mount. Check all bolts for the mounts and supports attached to the block and the frame. Using clevite or rubber mounts will transmit less road vibration from the engine to the unibody and feel like a smoother ride compared to polyurethane mounts.


I am sure that some of you will disagree with something that I have said. My intention is broaden your area of scrutiny if the problem has not yet been solved. In the end, one can theorize forever. Actually examining and attempting repairs are the only thing that will fix a problem. The purpose of discussion is try to make your efforts productive and reduce wasted effort, not to rag on each other's ideas.


Best of luck in solving this problem.
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  #48  
Old May 28th, 2019, 08:12
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Re: Clunk/lurch into Drive, but not Reverse

Solid info there
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  #49  
Old May 28th, 2019, 17:28
Drastik Drastik is offline
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Re: Clunk/lurch into Drive, but not Reverse

Hey gang, first post here. I had to register after reading this thread.

My 99 XJ does something very similar. It's a clunk and lurch when I put it in drive, but nothing in reverse.

I've noticed that mine is much louder/ harsher when I've been driving on the expressway for a while and the vehicle is hot.

It's much less pronounced when the vehicle is cold.

I'm curious if you've noticed this with yours op?

I just bought my XJ about a month ago, and I've never been much of a grease monkey so I'm hoping to learn alot on the forum, starting with this thread!

Thanks for sharing op.
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  #50  
Old June 9th, 2019, 08:25
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by Drastik View Post
Hey gang, first post here. I had to register after reading this thread.

My 99 XJ does something very similar. It's a clunk and lurch when I put it in drive, but nothing in reverse.

I've noticed that mine is much louder/ harsher when I've been driving on the expressway for a while and the vehicle is hot.

It's much less pronounced when the vehicle is cold.

I'm curious if you've noticed this with yours op?

I just bought my XJ about a month ago, and I've never been much of a grease monkey so I'm hoping to learn alot on the forum, starting with this thread!

Thanks for sharing op.
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  #51  
Old June 9th, 2019, 08:33
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

OP here...I haven't noticed a difference cold vs. hot. My question for you would be:
If you shift quickly directly from Reverse to Drive (without pausing in Neutral at all), does the clunk/lurch substantially reduce?

Mine reduces drastically to a very tolerable level whenever I do not pause in Neutral.

Quote:
Originally Posted by Drastik View Post
Hey gang, first post here. I had to register after reading this thread.

My 99 XJ does something very similar. It's a clunk and lurch when I put it in drive, but nothing in reverse.

I've noticed that mine is much louder/ harsher when I've been driving on the expressway for a while and the vehicle is hot.

It's much less pronounced when the vehicle is cold.

I'm curious if you've noticed this with yours op?

I just bought my XJ about a month ago, and I've never been much of a grease monkey so I'm hoping to learn alot on the forum, starting with this thread!

Thanks for sharing op.
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  #52  
Old June 10th, 2019, 18:27
Drastik Drastik is offline
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Re: Clunk/lurch into Drive, but not Reverse

I just got done skimming your other thread on this subject so I'll try that next time I get it out,( next weekend at the latest) and report back.
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  #53  
Old June 10th, 2019, 19:45
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Re: Clunk/lurch into Drive, but not Reverse

I did have something similar happen about 10 years ago. The pinion nut was backing off and the pinion would shift location. It ultimately took most of the teeth off of the pinion.
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  #54  
Old June 10th, 2019, 20:08
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

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Originally Posted by Drastik View Post
I just got done skimming your other thread on this subject so I'll try that next time I get it out,( next weekend at the latest) and report back.
OK, thanks. I should refer readers here to the other thread, since the "not pausing in Neutral prevents the clunk/lurch" is the latest discovery that I have made about the problem, and, I believe, the best clue as to what is causing the problem.This older thread was started before I discovered that.

Here is the newest "Please try this with your XJ and tell me results?" thread:
https://www.naxja.org/forum/showthre...#post246650204
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  #55  
Old June 12th, 2019, 18:49
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by dsbhealer View Post
The play in your rear axle, as shown in the video, is a major cause for concern. When you step on the brake and shift from neutral into gear, the power from the engine/ flexplate/ torque converter/ transmission/ rear driveshaft must go through the rear differential before it hits the rear brakes. Play anywhere along that path can cause problems. I had a problem with my 2000 xj where the bolts that hold the flexplate to the torque converter were loose and the holes wallowed out on the flexplate, causing part of my lurch from neutral to drive or neutral to reverse.

You can try an experiment to see if it is indeed the rear axle (from your video, it really looks like the rear axle to me). Block the wheels to prevent the jeep from rolling. remove the rear driveshaft from the rear axle pinion and then remove the driveshaft from the jeep by sliding it off the slip yoke. Put the transfer case in 4wd part time hi. With your foot on the brake, try shifting and see if there is less lurch and clunk with the front axle compared to what you were previously experiencing with the rear.
I just performed the experiment...thanks for the suggestion...now I think that I can say for sure that the problem is not the rear driveshaft, differential, etc. The symptoms never fit for the problem to be behind/beyond the transmission input shaft, but hey..you never know.
The clunk/lurch is pretty much identical using only the front differential, including the "rebound" clunk that you can see in the my old posted video of the rear driveshaft movement.
Using the front differential only, when I shift directly from Reverse to Drive without pausing in Neutral, I get one minor clunk, and when I pause in Neutral before shifting to Drive I then get the same "violent" clunk/lurch (and also the same rebound clunk) that I get when using only the rear differential.

Regarding my question about whether the transmission input shaft turns when the transmission is in Neutral, I tried this: With the rear driveshaft still removed, I used 2H and Neutral to see if the rear transfer case output shaft would be turning at all, and sure enough it spins VERY slowly and steadily...and I can easily stop it with my hand. So I'm assuming that this means that MY torque converter turbine and transmission input shaft ARE turning with the transmission in Neutral, because otherwise what would be turning the transfer case rear output shaft? One would think that Neutral would completely 100% disconnect the transmission input from output, but either that is not 100% true or only MY transmission behaves this way. I'll need to find out if other people's XJ's behave this way or not, I guess, to find out it this is normal or not.
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  #56  
Old June 12th, 2019, 20:02
lawsoncl lawsoncl is offline
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Re: Clunk/lurch into Drive, but not Reverse

Motor and tranny mounts still makes sense, because stopping in neutral lets the engine mounts relax before you load it again. There is no "disconnecting" in neutral like a manual transmission disengaging gears, just clutches/brakes that let the planetary carrier freewheel.
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  #57  
Old June 12th, 2019, 21:00
soyjer soyjer is offline
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Re: Clunk/lurch into Drive, but not Reverse

Quote:
Originally Posted by lawsoncl View Post
Motor and tranny mounts still makes sense, because stopping in neutral lets the engine mounts relax before you load it again.
Agreed...Neutral = Relaxation = Play = Clunk/lurch...that's why I've been skeptical of the problem being any component (transmission gears/output rearward) that reverses direction when shifted from Reverse to Drive.
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