Popping sound in 4wd...

I was off doing some trail riding for the first time in my Jeep I purchased about 2 1/2 months ago, when I heard a popping/ clunking sound coming from what sounded like the kinda front middle of the Jeep. It only does it in 4wd drive, and it sounds like it happens more in 4 low, and more when its under stress (such as steep incline, getting out of a trench, ect.) The guy that had it before me said that one of his friends thought that it needed a new U-Joint ( I bought it whoelsale from a dealer, but the guys number was in the Jeep). So, is it a bad u-joint, or am IO missing a tooth or something in my transfer case? It sounded like there was a chattering/clicking sound when I was driving back home in 2 wheel, but seems to have gone away.

EDIT: Besides the sounds, it seems to have done very well, I didn't have any loss of power or anything.

Yup definatly sounds like a bad u-joint to me. Grab the end of you axle shafts and check for any slop or play in the joints on both sides to confirm one or two needs replacing.

Mine's been doing that for ?-a long time. I don't know what it is either. Real random but it only happens under stress. Nice loud pop/bang like something it breaking. U-joints are fine.....gears are fine.....it did it b4 abd after my locker install. It definatly comes from the front end though.
Brett

I get that also (in my '88 - SelecTrac) but only going up hill in 4Lo . . . I think it's in the transfer case. My U-joints are, likewise, fine. I would liken it to something like a cone-type clutch that's popping/slipping or something . . . . I only use 4Lo when I absolutely have to and the problem manifests itself nowhere else (several years now) so, I haven't worried about it much. I think maybe it's related somehow to the fact I don't use it . . . . 'just ideas . . . . Don

I've had the same problem in my '90. But really only when going uphill or when I get on the gas, so basically only when I need it right? Anyway, I found that I had a bad U-joint. All the needle bearings under one of the caps were gone, maybe went to needle bearing heaven, anyway I replaced both the right and left with greasables from Summit Racing just last saturday. I did a search of the forum and found a really good step by step from CheifXJ?? I think. Anyway it was pretty easy and the popping sound has gone away plus I don't rock back and forth when making tight turns. However, the 4x4 still slips out, not as bad but one of the times it made a strange grinding noise like gears out of mesh or maybe the chain in the T-case?? A guy at a transmission place told me something about a plastic piece inside the T-case that often breaks and can cause what I described to him. $7 piece but $450 labor...go figure. Anyone else heard of this?? Maybe it's all of our problems...

I'm just moving this up . . . in the hope we'll all get a little more feedback/ideas. Don

sounds like maybe a streched t-case chain.

Digger87xj said:

sounds like maybe a streched t-case chain.

Click to expand...

I think I like the u-joint answer better, its cheaper.
:hang:

EDIT: If it helps, the Jeep popped out of 4lo when I was ging up a steep hill one time.

I had a 92 with that problem. It was U Joints. My 96 did the same thing but got a little quieter after driving it some, and my 98 I have now does it as well.
Its a Jeep Thing.

My 242 stretched it's chain and would make the same noise.

I guess I'm missing something re the "stretched chain" theory . . . . . . if that was it, wouldn't the problem manifest itself in situations other than 4 low under a load? Don

My '91 (np231) does something similar but usually only in the winter time but always up steep inclines. It does it in both 4wd and 2wd. With it happening in 2wd, could this be a stretched chain?

thanks
Dean

ps-sorry for the highjack

I quarantee its the chain
change the tcase chain
definitly

Okay . . . but, is there an explanation for why (in mine and, apparently others) this does not show-up other than in 4 lo and going up an incline? I haven't been into a tf case and am trying to better understand this. Thanks. Don

Don Becker said:

Okay . . . but, is there an explanation for why (in mine and, apparently others) this does not show-up other than in 4 lo and going up an incline? I haven't been into a tf case and am trying to better understand this. Thanks. Don

Click to expand...

By placing the t-case in 4 low,(and going uphill) you are effectively doubling the torque going to the tires.. this streches the chain to the point that it will jump teeth.
Drain your t-case and look into the drain hole witht a penlight... you can see the chain sagging... in many cases, it will also be contacting the case itself.

Another way to verify a stretched chain is to go out on the street and put it in 4lo...ride the brake as hard as you can while you give it gas, creeping forward..if the chain is streched it WILL jump.

CHAIN! Easy way to check this is put it on a lift (six pack to a garage and they will pobably let you do it after hours). When all wheels are off the gound, put it in 4 low and let the wheels rotate in gear. turn the wheel full right and left, if no popping it is probably the chain if you already checked the U-joints. An 88 will probably be streched pretty good if it was ever in 4 for long periods of time. The chain is easy to replace. The hardest/time consuming part is removing it from the XJ. Just start from the rear of the case and lay out everything in order that you took it appart. BUT while it is in the jeep, remove the front yoke first (nut holds it on) becasue it will be easier to lock it in place to put the pressure on it. I have seen cains run from 200 down to 50 used. many people have extras here. Matter of fact I had to do it with mine. Take pictures of it before completly taking it apart and work in reverse order when putting it back together. Plan a good part of the day to do it and you should be OK especially if you haven't done it before so you don't forget how things go back together.
Dan

Thanks for the great information . . . . now, I understand. Don