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  #1  
Old April 16th, 2019, 09:50
soyjer soyjer is offline
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Please try this with your XJ and tell me results?

1999 XJ, 98K easy (street-only) miles, 4.0L, AW4, Chrysler 8.25

With your XJ at a standstill, please try shifting into Drive from Reverse both WITH a pause in Neutral and WITHOUT a pause in Neutral, and let me know which gives you a smoother (even slightly) shift into Drive?

I (and several professional XJ and transmission experts) have now spent over a year trying to diagnose my XJ's "clunk/lurch when shifting into Drive at a standstill" problem (see below link if you want the gory details), and I now believe that the key to knowing whether it is the transmission or differential lies with whether or not "normal" XJ's make this shift smoother WITH a pause in Neutral or WITHOUT a pause in Neutral.

Mine makes this shift very smoothly if I do NOT pause in Neutral, but if I DO pause in Neutral then the clunk/lurch into Drive is comparatively rather violent.

The only explanation that I can come up with for this behavior would be that, when in Neutral, the input half of the transmission rotates freely at approximately the rpm of the engine, whereas when in Reverse, the input half of the transmission is held stationary by the stationary rear wheels on the ground, and so when in Neutral the input shaft has rotational momentum that causes the clunk/lurch when shifted into Drive, whereas when there is NO pause in Neutral then there is NO rotational momentum, and so there is no clunk/lurch when shifted into Drive.

But in order for this theory to be true, then ALL XJ's at a standstill must ALSO shift from Reverse into Drive smoother (even just a little bit) WITHOUT a pause in Neutral than WITH a pause in Neutral.

If ALL XJ's behave this this way, then my transmission is functioning 100% normally, and it is merely a loose differential that is amplifying this behavior in my XJ.

On the other hand, if pausing in Neutral does NOT result in a slightly harsher shift in normal XJ's than not pausing in Neutral, then my theory is bogus, and then that casts suspicion back onto my transmission, on which a complete professional rebuild didn't solve the problem.

If I could get the answer to my question here, and if it confirms that ALL XJ's behave this way (only to a lesser degree), then I will just have to assume that all of the experts were wrong about my differential, and pay one of them to look inside of it, even though they are saying that doing so is a waste of time.

https://www.naxja.org/forum/showthre...1146705&page=3
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  #2  
Old April 16th, 2019, 16:02
md21722 md21722 is offline
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Re: Please try this with your XJ and tell me results?

At the back of the transfer case/transmission there will be a slip joint under a black rubber boot. Removing the driveshaft and greasing the splines of this slip joint can eliminate a lot of clunks that might be attributed to a transmission or rear end.
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  #3  
Old April 16th, 2019, 17:39
Black1990jeep Black1990jeep is offline
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Re: Please try this with your XJ and tell me results?

Quote:
Originally Posted by md21722 View Post
At the back of the transfer case/transmission there will be a slip joint under a black rubber boot. Removing the driveshaft and greasing the splines of this slip joint can eliminate a lot of clunks that might be attributed to a transmission or rear end.
Some clunks as described happened on my jeep, greased it well, and clunks went away.


good luck
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  #4  
Old April 17th, 2019, 18:58
JeepNoob JeepNoob is offline
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Re: Please try this with your XJ and tell me results?

Couple of points here....

1. When diagnosing a problem with a vehicle, it is advisable to compare the condition to a like vehicle, I.E. same year, make, model, engine, transmission, etc. With an XJ, you're talking about a vehicle that was made, I dunno, what for 15 years with the last ones rolling off the line almost 20 years ago? LOTS of variance there in terms of parts, mileage, maintenance, etc.

2. Things are relative and subjective. This one kinda bit me in the butt when I used to work as a professional wrench-monkey. See, I'm used to old, rolling crap piles like XJ's. Never leased or taken out a loan on a vehicle in my life. When you drive old iron like that, you get accustomed to their... quirks. And when you get accustomed to it, you might just dismiss problems on a nicer, newer vehicle. For example, when I worked as a wrench-monkey at a shop, I took a job where the customer was complaining of a "whining" noise from the front of the vehicle (vehicle was a used Caddy Escalade, but still probably worth $40K or $50K) Took it for a spin, and it was hard to tell with my bad hearing, but it sounded like front wheel bearings. Got it back to the stealership shop and sure enough, both were starting to go out. The point here is, what you describe as a "violent shift," somebody like me might just chalk up to tired U-joints and put it on the long-term "to-do" list.

3. And for the record, I tried this on my POS '89, probably 5 or 6 times. I wouldn't describe any of the shifts as "violent" once the trans had some fluid pumping through it. (see point #2) Clunky, which indicates to me that the U-joints need some TLC and this tired old Dana 35 needs go back to the scrap pile of the foundry to be made it something better, but not "violent."
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  #5  
Old April 17th, 2019, 19:16
lawsoncl lawsoncl is offline
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Re: Please try this with your XJ and tell me results?

According to the AW4 manual, starting with the shifter in neutral moving it to reverse should have a maxiumum engagement time of 1.5 seconds, and moving to drive should have a maximum engagement time of 1.2 seconds. It also identifies the primary cause of harsh engagement as an improperly adjusted throttle-tranny cable. Have you adjusted that properly?
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  #6  
Old April 18th, 2019, 06:08
soyjer soyjer is offline
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Re: Please try this with your XJ and tell me results?

Original post explains extreme measures already taken to diagnose problem, including complete transmission rebild, etc.

Experts are stumped, so now I am just trying to follow my best "clue", which is simply that pausing in Neutral causes a harsher shift to Drive than not pausing in Neutral.
If my theory about input shaft momentum is correct, then this should be true for ALL AW4 transmissions, regardless of condition or age. The only difference would be the DEGREE OF NOTICABILITY between pausing and not pausing. On XJ's with tight drivetrains, it should be HARD to detect the difference, whereas on XJ's with LOOSE drivetrains, it should be EASY to detect the difference, if my theory is correct.
If I had a 2nd XJ here...preferably one with a loose drivetrain, then I could answer my own question, but I don't know anyone here with a Jeep of any kind, and so I'm trying to get an answer or two from this forum.
If my theory is correct (ALL AW4's behave this way, only to varying degrees), then all of the professional mechanics saying it's the transmission are wrong, and it is just my loose drivetrain that is merely AMPLIFYING the normal behavior of the AW4.
On the other hand, if my theory is bogus, then the transmission shop that rebuilt/replaced my transmission/torque converter managed to somehow accomplish that without fixing the clunk/lurch problem.
Either of the above would require that multiple experienced, honest, reputable, professional mechanics somehow were ALL wrong in their diagnoses of this problem, which is also hard to believe.
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  #7  
Old April 19th, 2019, 08:09
MickeyS MickeyS is offline
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Re: Please try this with your XJ and tell me results?

On my 96, going into D quickly from R causes a huge lurch/shock to the driveline, and stopping in neutral can eliminate it sometimes. I greased the slip yoke which helped slightly, however the issue I believe is wear and tear on the original driveshaft/pinion/axle/slip yoke over 200k miles. lots of little things with a tiny bit of play add up once you count every component.

I removed the driveshaft and drove it around in 4wd and the situation improved 90% very little lurch, the rest I'm guessing just a worn front driveline.

I'm totally guessing here, but once I do a SYE, replace driveshafts, do my axle swap, the problem will go away entirely.
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  #8  
Old April 19th, 2019, 09:11
soyjer soyjer is offline
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Re: Please try this with your XJ and tell me results?

Thanks for the doing the test for me... your results would seem to indicate that my transmission is behaving in the exact opposite manner to a normal AW4.
The real mystery is what could possibly cause it to be doing this, and how did the transmission problem "survive" a complete professional transmission/torque converter rebuild/replacement? The transmission mechanic even, out of desperation, finally replaced the transmission CASE...and (of course) that didn't fix the problem, either. :-(

Quote:
Originally Posted by MickeyS View Post
On my 96, going into D quickly from R causes a huge lurch/shock to the driveline, and stopping in neutral can eliminate it sometimes. I greased the slip yoke which helped slightly, however the issue I believe is wear and tear on the original driveshaft/pinion/axle/slip yoke over 200k miles. lots of little things with a tiny bit of play add up once you count every component.

I removed the driveshaft and drove it around in 4wd and the situation improved 90% very little lurch, the rest I'm guessing just a worn front driveline.

I'm totally guessing here, but once I do a SYE, replace driveshafts, do my axle swap, the problem will go away entirely.
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  #9  
Old April 19th, 2019, 10:13
MickeyS MickeyS is offline
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Re: Please try this with your XJ and tell me results?

these issues are common on an XJ. I'd just deal with it the way it is. they're starting to show their age now and will have little quirks like this.

do you have 4x4? get underneath and pull the driveshaft. it's not difficult. then stick it in 4x4 and drive around cautiously in a parking lot at low speed. go into r/d/n. see if the problem goes away. if so, there's slop in the rear end driveline.
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  #10  
Old April 19th, 2019, 11:11
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ShoeterMcgav ShoeterMcgav is offline
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Re: Please try this with your XJ and tell me results?

Probably already been done... But how do the motor mounts look?

How does it respond to the initial P to R? And P straight to D?
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  #11  
Old April 19th, 2019, 13:44
MickeyS MickeyS is offline
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Re: Please try this with your XJ and tell me results?

Quote:
Originally Posted by ShoeterMcgav View Post
Probably already been done... But how do the motor mounts look?

How does it respond to the initial P to R? And P straight to D?
good point. check mounts
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  #12  
Old April 19th, 2019, 17:51
trippled trippled is offline
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Re: Please try this with your XJ and tell me results?

Driven a lot of xjs that exhibit this. Never once thought it was bad to address. A lot of the problem I notice too is worn/soft springs. In reverse the axle rotates down, effectively flattening the springs (and the axle trying to move rearward from reverse) and slightly lowering the vehicle. Going to drive the opposite happens and the springs unload slightly, giving a little bit of clunk/lurch. Seems worse cold when the idle is high as it's exaggerated slightly.

Wouldn't be bad to make sure all your suspension is in good order.

I totally agree tho, one person's horrible clunk is another's...eh.
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  #13  
Old April 19th, 2019, 18:14
soyjer soyjer is offline
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Re: Please try this with your XJ and tell me results?

Quote:
Originally Posted by MickeyS View Post
these issues are common on an XJ. I'd just deal with it the way it is. they're starting to show their age now and will have little quirks like this.

do you have 4x4? get underneath and pull the driveshaft. it's not difficult. then stick it in 4x4 and drive around cautiously in a parking lot at low speed. go into r/d/n. see if the problem goes away. if so, there's slop in the rear end driveline.
I have no doubt that the clunk/lurch would totally disappear without the rear drivetrain connected, because anytime that the XJ is rolling at or above the speed that it would normally be traveling at idle rpm in Drive, then the clunk/lurch does not occur, whether I pause in Neutral or not. It's like striking an anvil with a hammer...no anvil, no clunk.

The clunk sound DOES sound as if someone is hitting the differential ring gear with a hammer, which may well indicate that ALL OF THE EXPERTS ARE WRONG and the driveline somehow has excessive play, but even if it does, that doesn't explain why MY transmission shifts smoother without a pause in Neutral, whereas seemingly all other AW4's shift smoother WITH a pause in Neutral. That fact is the ONE SOLID clue that I have that my XJ is different than a normal XJ, and that is why I am pursuing that first.

What I need is for fellow AW4 owners to just try the test that I am requesting (takes about 10 seconds) and report the results, so that I can confirm that MY AW4 prefers NO pause in Neutral whereas everyone else's AW4 prefers a pause in Neutral.

So far only one reader here has done this test, and I would feel more confident if I heard it from more than just one AW4 owner before I pay $2000+ dollars to have my transmission rebuilt (again!).
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  #14  
Old April 19th, 2019, 18:23
soyjer soyjer is offline
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Re: Please try this with your XJ and tell me results?

Quote:
Originally Posted by ShoeterMcgav View Post
Probably already been done... But how do the motor mounts look?
How does it respond to the initial P to R? And P straight to D?
I paid a reputable shop here $90 to SPECIFICALLY look at the entire drivetrain, all mounts, etc., and they said that it all checks out OK and "it's the transmission".
Additionally, the transmission shop had it INSIDE of their shop for 9 weeks, completely rebuilt the transmission, replaced that torque converter, even the transmission case, etc., and didn't even charge me a penny for the normally $2200.00+ job (because he said that he doesn't charge for work that doesn't solve the problem)! It's hard for me to believe that they would have invested that kind of time and money into the transmission without even looking at the rest of the drivetrain, mounts, etc.

It' not IMPOSSIBLE that ALL of the shops that have looked at this are all wrong....but it's not LIKELY, either. The ONE SOLD clue that I have in all of this is this pausing in Neutral thing...and that is why I am trying to get an answer from other AW4 owners about this one specific thing.
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  #15  
Old April 19th, 2019, 18:27
soyjer soyjer is offline
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Re: Please try this with your XJ and tell me results?

Quote:
Originally Posted by ShoeterMcgav View Post
Probably already been done... But how do the motor mounts look?

How does it respond to the initial P to R? And P straight to D?
The ONLY way to cause the clunk/lurch is to pause in Neutral before shifting to Drive (at a standstill, from any other gear, or Park). There is NO other way to cause the clunk/lurch.
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