Clunking only in 4wd, not ujoints

I had some issues with loud clunking that was really bad in 4wd few months ago, pulled the front shaft thinking it was u-joints in that, turned out to be passenger side axle u-joint. Replaced that and have been riding with no front shaft for about a month with no issues.

Heard snow was coming so i put my front shaft back in last night- only to find a similar horrific grinding noise when in 4wd, and slowly turned into a tick in 2wd. Looking for suggestions as to what it might be.

Replaced the passenger front axle u-joint, driver's side appeared, and feels solid. After replacing that my initial clunking stopped. Replaced the front u-joint on the front shaft, the two in the CV portion looks and feels solid. Also replaced both u-joints in the rear shaft, since one was cracked.

The "clunking" exhibits the same type of noise a toasted u-joint does- a clear 'clunk-rotate-clunk-rotate' that increases intensity with speed, and not with engine RPM. When the front shaft was out, no abnormal noise was made when placed in 4wd (granted yes, there was no load).

About a month ago i stuck my finger in the front diff to check for fluid, remember there being plenty, and a slight silver color. Worse case scenario here i'm thinking is the front diff is toast. Aside from pulling the front cover (currently snowing like a bitch), any other tip on confirming blown gears?

Any input is greatly appreciated.

1992 XJ, 4.0l, 5spd, NP231, 3.07 gears, 250,000 miles, drive train is stock, 3" lift on 31's

Went out and played with it a little bit. You can feel the clunk in the transmission shifter, but not in the TC shifter... which i thought was odd. I had my brother drive up and down the block while i scurried along the ground, nothing looked like it was binding, or shifting out of normal. Everything "looked" tip top. It was very hard to hear the sound outside the jeep because of the exhaust (no tailpipe after the cat), but is Loud and discomforting inside the cab.

Does it in both forward and reverse gears. Hard to tell if it's any worse when turning cause of the 4wd pop on the pavement. Is it likely that the double joint at the rear of the front shaft has bad u-joints, but look and feel solid?

I started to unbolt the front shaft from the TC, but stopped quickly out of frustration- the fact that damned metal ring is in the way preventing a ratchet is ridiculous. After this post i'm going to head up to sears and get some baby ratcheting wrenches, rather use a smarter tool then get pissed at a bad design, lol.

I'm assuming it would be a bad idea to change diff fluid while it's raining? Wanted to do that, but it's been raining non stop all day.

The loudness inside the cab and the shifter feel make me now think it's the TC vs the front diff. I'm hoping by the time i get back to the house someone will have a suggestion for me for something to try.

My first suggestion is to move to a warmer climate, it's too early for snow.

Have you jacked the front end up and spun the wheels by hand while looking and listening?
I had a terrible front end noise that took several tries before narrowing it down to a bad pinion bearing. You barely heard it in 2WD and was terrible in 4H. There was no noise with the driveshaft removed.
If you saw silver in the oil, there is a good chance the front axle is damaged and you check it out. Pulling the cover is the best way. If it is bad, replacing the whole axle with a JY unit could be the quickest and maybe the cheapest way of getting it back on the road before the real winter sets in.

I have this exact problem right now, the clunking in 4 wheel, after a while, or listen close you'll hear a light noise. My problem is a stretched transfer case chain. My biggest clue was rolling the front shaft and hearing the slapping in the case. Good luck.

Too early for snow!? I was surprised it didn't snow mid October. lol.

I haven't had a chance to put it up on jackstands yet, our jack has been commandeered by a friend...

shawnhancel said:

My biggest clue was rolling the front shaft and hearing the slapping in the case. Good luck.

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That chain is what i'm fearing.. I may give this a try here in a few, just getting back home. I assume it's a unhook front diff, put in neutral, then spin with hands?

disconnect the front d/s and spin the transfer case yoke by hand

if its a c.a.d. axle the selector may not be sliding the collar over far enough and its slipping....the aluminum fork from the factory wears out pretty easily...took me awhile to figure that out...

bigdummy30 said:

if its a c.a.d. axle the selector may not be sliding the collar over far enough and its slipping....the aluminum fork from the factory wears out pretty easily...took me awhile to figure that out...

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It's not a c.a.d. axle, solid axle shafts both sides.

I was at a friends house helping my brother install his alarm, and was able to pull it inside and at least take my front shaft back out so i can continue driving it. I took a few videos of my rotating the TC output and pinion on the diff. It all seemed like normal play to me, aside from a bit of hollowness that may be attributed to low fluid in the TC. I am attempting to upload those to photobucket as we speak, they are huge videos (thank you Samsung EPGT.)

The pinion fluid wasn't quite as silver as i remember it, unless any particulates settled in the cold...

I didn't have the fore sight to take a video to see if I could capture the sound on video, but it was pretty close to the "4lo trans 1st" video i plan on getting up here soon, only at a rapid pace based on tire speed (independent of engine RPM).

Thanks again for your input guys. My next steps are going to be pulling the front diff cover and checking any catastrophic damage, and obliviously replace the fluid. Then get it up on jack stands when i can track my jack down..

Sticking my pinky in the front diff cover. Drips on paper towel are from that pinky dip.


Video of another pinky dip.


Video of rotating pinion with hand. No abnormal noise, grinding or general weirdness. Pushed hard enough to roll jeep forward about 6in with no apparent teeth skipping or roughness.

Following videos were with the vehicle on the ground with front shaft pulled.


TC in 2wd with transmission in neutral.




TC in 4wd Hi with transmission in neutral.




TC in 4wd Lo with transmission in neutral.





TC in 4wd Lo with transmission in first gear.

SPIN the TC output shaft instead of just knocking it around. Do it in 2WD. You want to hear if the chain is rubbing or if the engagement is slipping. Pretty common problem for these things to stretch the chain and/or have a lockring snap and the mainshaft starts walking back and forth.

and don't use 4wd on dry pavement "...Hard to tell if it's any worse when turning cause of the 4wd pop on the pavement..." <----- a 4wd pop on dry pavement is the t-case binding. If you think it is ok and normal to drive on pavement while in 4wd, then you probably have been done this before. your tcase probably hates you and the chain is stretched. Both your driveshafts spin at the same rate when 4x4 is enagaged; your tcase is basically acting as a locker between your axles. When you turn, your front driveshaft spins at a different rate than the rear, and your tcase binds (chain stretches).

ehall said:

SPIN the TC output shaft instead of just knocking it around. Do it in 2WD. You want to hear if the chain is rubbing or if the engagement is slipping. Pretty common problem for these things to stretch the chain and/or have a lockring snap and the mainshaft starts walking back and forth.

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Ok, when you guys say "spin," you arent specificing the parameters. 1st? 2nd? 3rd? 4lo? 4hi? On ground, on jackstands? With AM, or FM on? The first video has the transmission in neutral and the TC in 2wd, no noise whatsoever and spins freely. I stated the jeep was still with all four wheels on the ground, havent gotten it jacked up yet.

bdahlg said:

and don't use 4wd on dry pavement "...Hard to tell if it's any worse when turning cause of the 4wd pop on the pavement..." <----- a 4wd pop on dry pavement is the t-case binding. If you think it is ok and normal to drive on pavement while in 4wd, then you probably have been done this before. your tcase probably hates you and the chain is stretched. Both your driveshafts spin at the same rate when 4x4 is enagaged; your tcase is basically acting as a locker between your axles. When you turn, your front driveshaft spins at a different rate than the rear, and your tcase binds (chain stretches).

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I understand you aren't supposed to tool around every day on pavement, but sometimes its the only way to test if it's actually in 4wd, or to see if a front u-joint is out without tearing the whole thing down. I've only done it a handful of times in the five or so years I've owned it, can't vouch for the previous owner on the other hand. With 250,000mi and Nebraska on/off winter who knows.

As of right now stretched chain in what I'm banking on, but I sure as hell haven't driven it on payment enough to toast it. On road I prolly only use 4wd two or three times a winter, and that's with snow/ice.

You have a '92, therefore your D30 is not a CAD. This means you front driveshaft spins whether you're in 4x4 or not. If it is makng the sound when you pull the shift lever into 4x4, this narrows it down to the tcase, especially since you pulled the front driveshaft already. The innards of an NP231 are fairly simple. I would venture to guess that the chain is stretched, and the popping comes from it skipping teeth.

I would raise the jeep up on all fours with jackstands and test from there. This is really the only way to test the tcase in every way possible. Then you can put it in to any gear you want and narrow it down further.

bdahlg said:

You have a '92, therefore your D30 is not a CAD. This means you front driveshaft spins whether you're in 4x4 or not. If it is makng the sound when you pull the shift lever into 4x4, this narrows it down to the tcase, especially since you pulled the front driveshaft already. The innards of an NP231 are fairly simple. I would venture to guess that the chain is stretched, and the popping comes from it skipping teeth.

I would raise the jeep up on all fours with jackstands and test from there. This is really the only way to test the tcase in every way possible. Then you can put it in to any gear you want and narrow it down further.

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One main thing I was curious about- will a slapping chain still slap in 4wd with the front shaft taken out? Without the front shaft in it makes no noise, ever. I know without load the dynamics change, but didn't know if that the stretched chain would should symptoms regardless.

fattmann said:

One main thing I was curious about- will a slapping chain still slap in 4wd with the front shaft taken out? Without the front shaft in it makes no noise, ever. I know without load the dynamics change, but didn't know if that the stretched chain would should symptoms regardless.

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I wouldn't think so. As you said, without a load on the pinion, it probably would not make a sound. Maybe you would hear it slapping, but it probably wouldn't be as severe and most likely would not be popping.

Makes sense. Will try to get it jacked up today between classes.

Side note- I was looking at my fill/drain plugs on the TC, the drain plug looks fine, but the fill plug looks like it might be about stripped. Didn't know if i should bother topping the off, or just wait till I diagnosis definitely, which may facilitate removing the TC housing anyway.

If it is the chain, I hear it's about the same cost/effort to replace the chain as it is to get a whole TC from upullit, that sound about right?

Yea, it will probably be cheaper/the same to pull a case from the junkyard than buy a new chain, depending on the pricing at the yard, etc

Don't think I'll have time to jack it up today, but noticed a weird noise on the interstate. When driving 50+ and accelerating, if I let off the throttle to coast I feel a quick vibration, then nothing. At first I thought it might be binding on the rear ujoints, but checked and saw no wear.

I usually have my music on so don't know how long it's been doing it, left my face plate home today lol. It made me wonder if that was the chain slacking out as the load shifted from acceleration to coasting. Just a thought.

fattmann said:

One main thing I was curious about- will a slapping chain still slap in 4wd with the front shaft taken out?

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The way these things work: There is a long (main) shaft that connects the transmission input to the rear output, a short shaft that only connects to the front output, and a chain that connects the two shafts together. When the vehicle is in 2WD, the chain is disengaged and only the rear output is driven. When the vehicle is put in 4WD, the chain is engaged and both shafts are driven.

However the front and rear driveshafts are permanently engaged to the axle differentials, so both driveshafts always turn, and therefore both of the transfer case output shafts also turn. So if the vehicle is in 2WD then the front output shaft will still turn, and it will also pull the chain, but the chain will not be engaged with the main shaft so it will only free-spin inside the transfer case.

If you disconnect the front driveshaft and run around in 2WD then the front output shaft (and the chain) will not turn at all.

The point of asking you to spin the front output shaft while the transfer case is in 2WD and the driveshaft is disconnected is to see if the noise is coming from inside the transfer case. If the transfer case is in 2WD then it does not matter what gear the transmission is in since the chain will be disengaged from the main shaft anyway. If you still hear noise in this state, then the chain may be dragging on something, or another possibility is that the sprocket is partially engaging (such as a broken lockring that allows the main shaft to move around inside the case where it can partially engage the sprockets).

If you don't hear the noise while spinning the output shaft, then look elsewhere.