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Please try this with your XJ and tell me results?

Just had to move the MJ after doing the exhaust. Virtually no clunk at all. My idle was also a little lower than normal after installing the exhaust versus the previous missing everything past the cat. I also checked the play in the rear pinion. About 1/4" along the diameter twisting by hand in neutral with parking brake on. Similar to yours really.
 
Could a stretched TC chain cause this? You said its never been opened. my jeep has always lurched into gear before and after regear, front or rear drive shaft only in place.

O.p. rebuilt/ replaced trans, what about tc & still interested in the previously mentioned diff inspection as well.

Are you aware of all fluid levels being correct and measuring correctly?
 
Thanks, but I'm still hoping to find someone whose vehicle (doesn't even have to be a jeep) exhibits the same "clunk/lurch only happens after a pause in Neutral" behavior, because it doesn't seem logical that the differential/driveline would suddenly become OK every time I avoid pausing in Neutral.
 
I do appreciate all of the advice that I have received, but the bottom line for me is this:
If my differential/driveline (not the transmission) is the problem, then why aren't other owners ALSO able to completely eliminate THEIR clunk/lurches by simply avoiding pausing in Neutral, just as I am able to do?
 
Thanks, but I'm still hoping to find someone whose vehicle (doesn't even have to be a jeep) exhibits the same "clunk/lurch only happens after a pause in Neutral" behavior, because it doesn't seem logical that the differential/driveline would suddenly become OK every time I avoid pausing in Neutral.

My 04 cummins ram with a 48RE trans does the same thing.
 
Can you post a picture of your motor mounts and maybe a video of the engine movement when shifting? Seems like a lot of us suspect you have a problem with the engine or transmission mounts and this might help convince them.


Maybe have a friend shift back and forth while you listen underneath for the source of the noise?
 
Can you post a picture of your motor mounts and maybe a video of the engine movement when shifting? Seems like a lot of us suspect you have a problem with the engine or transmission mounts and this might help convince them.
Maybe have a friend shift back and forth while you listen underneath for the source of the noise?

The Spock quote above is undeniably true, but, to me, the transmission input shaft forward to the motor mounts definitely makes the most sense as the source of the problem, because of the fact that everything behind reverses direction when shifting from Reverse to Drive.
Multiple shops (including a 2nd transmission shop I took it to a month ago) have checked the motor mounts and they ALL still point to the transmission, and I have, too, but I have no problem posting a video (it's free).
I've been studying transmissions and torque converters, but I still haven't answered this question:
When an automatic transmission (especially the AW4) is in Neutral, does the input shaft spin as the impeller continues to drive the turbine, or is there some mechanism that holds the input shaft stationary?
If held stationary, then a failure of that mechanism could cause my symptoms, because the inertia of that spinning input shaft would then be present in Neutral but not in Reverse nor Drive ( all with vehicle stationary).
Same result that loose motor mounts would cause.
 
Does your idle speed kick up when pausing in neutral? Usually, in reverse, engine has load, iac is open more to maintain idle speed. Then neutral the idle speed goes until it readjusts.
 
Does your idle speed kick up when pausing in neutral? Usually, in reverse, engine has load, iac is open more to maintain idle speed. Then neutral the idle speed goes until it readjusts.

Idle speed in Neutral is ~730 rpm.
I understand and agree with your logic...all other factors being equal, if Neutral rpm far exceeds in-gear rpm, then pausing in Neutral could indeed deliver a larger wallup to the transmission output shaft when then shifted into Drive, vs. shifting without the pause in Neutral.
I'll double-check my in-gear idle rpm. Thanks.
 
I've been studying transmissions and torque converters, but I still haven't answered this question:
When an automatic transmission (especially the AW4) is in Neutral, does the input shaft spin as the impeller continues to drive the turbine, or is there some mechanism that holds the input shaft stationary?


The pump is always driven by the torque converter. The t/c has two sets of splines. One set is connected to the outside of the t/c body and always runs at engine rpm and drives the hydraulic pump. The second inner set is connected to the inside of the t/c and is the part that "slips". When the t/c lockup solenoid engages, these two lock together by means of a clutch in the t/c which prevents the normal slipping of the t/c.


I PM'd you some info on what the shafting and gearing looks like and which clutches are engaged when. In neutral all but one clutch is engaged and that's the clutch that disengages to give you OD.
 
The pump is always driven by the torque converter. The t/c has two sets of splines. One set is connected to the outside of the t/c body and always runs at engine rpm and drives the hydraulic pump. The second inner set is connected to the inside of the t/c and is the part that "slips". When the t/c lockup solenoid engages, these two lock together by means of a clutch in the t/c which prevents the normal slipping of the t/c.
I PM'd you some info on what the shafting and gearing looks like and which clutches are engaged when. In neutral all but one clutch is engaged and that's the clutch that disengages to give you OD.

Thanks...I do have the manual, but no info there about any mechanism dedicated to stopping input shaft rotation in Neutral (and Park?).
A shop owner/mechanic told me that there is such a mechanism in an AW4, but he referred me to a transmission shop that said no. Seems to be my typical experience, these days. If I can't find the answer online, I'll visit our local community college auto shop...maybe they will know.
 
Looking at the diagrams, the carrier just spins but isn't driving anything because none of the clutches are engaged. I don't see anything that would deliberately brake the input shaft, or that it would matter. How is the adjustment on the throttle body cable? If that's real tight you can get some harsh engagement.
 
Looking at the diagrams, the carrier just spins but isn't driving anything because none of the clutches are engaged. I don't see anything that would deliberately brake the input shaft, or that it would matter. How is the adjustment on the throttle body cable? If that's real tight you can get some harsh engagement.

Throttle cable has lots of puzzled mechanic's fingerprints on it...that's where their adventure begins, and then line pressure, motor mounts, differential, etc....then they say "transmission" and send me to transmission shops that are just as puzzled after repeating same checks and tests, basically.

My feeling that an un-braked input shaft in Neutral could cause the problem is based upon the momentum of the spinning input shaft in Neutral vs. no momentum of stationary input shaft in Reverse or Drive. Not saying it's necessarily the problem or that such a braking mechanism even exists...only saying that it fits the symptoms because pausing in Neutral is what causes the clunk/lurch to occur.
 
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 above...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.
 
Even with the trans and/or tcase in neutral there's still enough "drag" throughout the system though fluid and friction of other parts to cause things to turn when no resistance is applied to them.
 
Even with the trans and/or tcase in neutral there's still enough "drag" throughout the system though fluid and friction of other parts to cause things to turn when no resistance is applied to them.

Thanks...yes...and of course, that would be true only if the torque converter turbine and transmission input shaft turn when the transmission is in Neutral...which I believe is true, and normal...but so far I haven't been able to verify that 100%.
Have you ever tried disconnecting the rear drive shaft, placing the transfer case in 2H and transmission in Neutral, and then seeing if the transfer case rear output shaft is very slowly and steadily turning, and then tried successfully to stop it by grabbing it, and then if you let go it starts turning again?
If you, or someone else, has been able to do this, then that would mean that it is likely normal for the torque converter turbine and transmission input shaft to turn when the transmission is in Neutral (in other words, there is no mechanism in an AW4 whose sole purpose is to stop the input shaft from turning in Neutral).
If it is normal for the torque converter turbine and transmission input shaft turn when the transmission is in Neutral, then that will eliminate one more possible source (input shaft momentum in Neutral in my AW4 that isn't supposed to be there) of my problem.
My motor mounts have been checked now by at least half a dozen professional mechanics, both general shop mechanics and transmission shop mechanics, but bad motor mounts sure do seem fit my symptoms...I'll make a video of my engine while shifting and post it here. Thanks.
 
Thanks...yes...and of course, that would be true only if the torque converter turbine and transmission input shaft turn when the transmission is in Neutral...which I believe is true, and normal...but so far I haven't been able to verify that 100%.




It's getting confusing with you running two threads on this. Yes, it is perfectly normal for the transmission output to freewheel a little bit in neutral when nothing is holding it.
 
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