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Diagnosis and fix of popping sound (from transfer case?)

lweiman

NAXJA Forum User
Location
Golden, CO
Ive got a 1991 Cherokee 4.0L, 5 speed manual, not sure what transfer case it has but the jeep is the base model.

Im a teenager and this was the First manual I've ever owned so of course I burned rubber around town. The problem is I popped the clutch at high RPM trying to take off fast one too many times and damaged something in my drivetrain and I do not know what.

Whenever I use an extraneous amount of horsepower (whether it be accelerating quickly or going up an incline with a lot of weight in the jeep) I hear a popping sound coming from the drive train.

It does not make this sound when I go up low inclines or take it easy on take-offs. I can drive it around town nice and easy and not have any problems with it.

I was in 2 wheel drive when I popped the clutch to damage it.

The sound is made when I am in 2 wheel drive, 4 low and 4 high.

At first I thought I broke a tooth on a gear, but realized there are a lot more weaker things in the drive train that would fail under stress before a tooth of a gear would.

I have been informed that this may be a transfer case chain being stretched.

Do you have any ways to troubleshoot my problem and pin down exactly what has happened?

Thanks,
A new jeep lover who's first jeep needs some help :(
 
Do a search on u joints. That might be the first thing to go in a high impact environment for that year. Or us google to diagnose bad u joints.

Check your leaf springs in the back for breaks.
 
it sounds to me like the chain in the transfer case is stretched, mainly because it makes the sound only when it's under heavy load. a broken gear or a worn ujoint would make the noise all the time.

your tcase is a 231 if you only have a part time 4x4 option on the 4wd shifter, it is a 242 if there is also a full time option in addition to the part time.
 
The sound is made when I am in 2 wheel drive, 4 low and 4 high.


If this happens in 2WD it should not have anything to do with the chain in the T-case.

If it were me, I would look at the motor mounts and make sure there is no rubber missing or cracks up front. If you are positive it is coming from the t-case area then maybe the Transmission mount has broke loose.

Please correct me if I am wrong about the chain...
 
I checked the U-Joints and they are good (there is no play in the drive shaft when I tried rotating it with my hands). Can you post a picture of what motor mounts are supposed to look like? Because I am not sure if mine are in good condition or not. I will post pictures of mine to double check.

And also can you give me an explanation of exactly where the transmission mount is?
 
I checked the U-Joints and they are good (there is no play in the drive shaft when I tried rotating it with my hands). Can you post a picture of what motor mounts are supposed to look like? Because I am not sure if mine are in good condition or not. I will post pictures of mine to double check.

And also can you give me an explanation of exactly where the transmission mount is?
 
91to99 is correct about the chain. The chain only comes into play in 4-wheel drive. If the noise is present in 2wd, then check the engine and transmission mounts and springs. you might want to pop off the rear diff cover and have a look-see in there for damaged ring/pinion gears as well.
 
These are my motor mounts, I do not know what to look for to see if they are in good condition or not. any advice?
7184399103


Can you tell me where the Transmission mounts are and how to tell if they are in good condition or bad?

I am sure chiltons will tell me how to go about taking the rear diff cover off? (draining fluid an such?)
 
The transmission mount is on the crossmember connected to the t-case.
Look for cracks in the rubber and I usually shake the drive shaft up and down to see if there is an excessive amount of play in the mount.
Visually your motor mounts look like they are in good shape, as long as the other one looks the same.

To drain the rear diff I take all the bolts out except one at the top and 2 near the bottom.
Then loosen those bolts till 1/4 in or so threads are showing.
Place an oil pan in the appropriate position and pry it open with a screw driver.

Your axle should be on jack stands so that you can rotate the internals and look for a broken tooth on the ring gear, spiders, and pinion.

I would think that if it were a bearing that is bad you would get a hum or grind while driving.

Another thing that you can do is see if you can replicate the problem by carefully power braking while in reverse and drive. Open the hood to see if your engine moves at all. You can also take a peek from a distance to see if your leaf spring bushings are moving/bad.

Is there a lift on the vehicle?
You may want to check out the Colorado chapter and see if any of those guys could help you out.
http://www.naxja.org/forum/forumdisplay.php?f=95
HTH
 
left, worn but still good (passenger side mount) right, bad mount (drivers side).

CIMG4147.jpg


drivers side usually goes first due to the directional torque of the engine rotation pulling the rubber apart.
 
I have concluded that it does not make the popping sound in 2 wheel drive after all. It only makes that popping sound in 4 wheel drive. This leads me to believe it is the chain in the transfer case that is stretched out.

Is there a guide on these forums somewhere about how to drop the transfer case and get inside and replace that chain? I need to get it done within a couple weeks, as I am going on a trip a couple hundred miles away and do not want to put more high rpm miles on that component

ALSO, When I am at high speeds in 2wd (almost always 5th gear, and sometimes 4th gear if i am going fast enough), I hear some "relaxed grinding" coming from what seems to be the transfer case. I think it would be the stretched out chain in there grinding on the side of the case. I am worried about some collateral damage that chain may have caused inside the transfer case (ie wearing through walls of the transfer case, or wearing through things inside the transfer case). Has that happened to anybody in the past when their transfer case chains stretched out?
 
Clutch and throwout bearing maybe, if your lucky!!!

Edit, never mind, just read your update.
 
i dont know if the 91 has the vacuum disconnect on the front axle. might have some bad vacuum lines going to it and its not fully engaging.
 
It is definitely the transfer case chain. and it is engaging, but i can hear the chain slip from ( i imagine) one tooth to the next with a very recognizable pop when I put lots of load on it
 
You've got a good mechanical mind for not knowing where a trans mount is.. :D That's exactly right, the chain skips, chains worn enough to skip have been known to wear right through the tcase housing. Even in 2WD as it is still spinning but carrying no torque.

There's no need to remove the tcase altogether for chain replacement. 231's are very simple inside, just mind the oil pump under the rear extension housing and its feed tube. If you do want to remove the unit to work on it a short 9/16 GearWrench works wonders.
 
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