I need all suggestions for what may be causing a loud clunking noise. It is a metal on metal banging noise that only happens when I'm in 4WD (hi or low) and under power. Doesn't seem to matter if I'm going up or down, flexing the suspension or not.

I have a '91YJ, 6cyl, front Quick-Lock, rear ARB, with 4.10 gears.
And no, it's not the front locker. This noise existed beore I put it in. :flipoff2:

:zzz:
driver's side motor mount

It can't be the driver's side motor mount. A motor mount "clunk"would happen under power in 2WD or 4WD. But this only happens when in 4WD. Make another guess:rasta:

uhhh.. the nut behind the wheel? :flipoff2:
I guess you might be right, my motor mounts would only bang in low range.
I give up then.

When my motor mounts went bad last year they were replaced with Currie 1" MM. To check MM, I had a friend look at the engine while I stepped on the brakes and revved the engine while releasing the brakes a bit. You could see the engine jump

I'm thinking the clunking is more front driveline related since it only happens in 4WD.

Would a bad ring/pinion tooth cause a loud clunking? Could my T-case (NP231) chain be skipping?.

Checking the front driveshaft, it has no up and down wiggle to it

not saying its it..but on my front 30 when i still had it adn the arb the case bolts are notorious for backing out..it let my center pin drop..after awhile it would drop down hit the pinion gear....and then it would get shoved back up there...i thought it was coming from the transfer case for a long time until it got worse.

also if you still ahve it check your track bar...mine was making a clunk like that and i removed the track bar and it stopped:D

Two things:
1. Your t/case chain in the crappy 231 has stretched. Get this fixed asap if it is or you'll damage the case badly :(
2. Yer stereo ain't loud enough :flipoff2:

I've got a Quick-Lock (basically a Lock-Right) in my D30. I put it in two weeks ago. BY case bolts I assume you mean the bolts that secure the ring to the carrier. I lock tightened these and torqued to spec (55ft-lbs, if I remember). The bearing caps also tightened to spec (also 55ft-lbs)
I can't be the front locker because this clunking happened b4 the locker was put in.
I did inspect the ring gear and saw no broken teeth. Did't get a good look at the pinion however:rolleyes:

Supergyper, What are track bars? Oh you mean those useless pieces of steel I threw away long ago. I don't have them front or rear and don't miss them

Wooders, I guess I'll be installing a new chain. I've got 82K on the current one and what the hey, I need to tear apart the T-case and stop the leaking anyways.

So a stretched chain would slip only while in 4WD since thic is the only time there is a load on it, right?

If it is loose enough to slip you would have other problems. Check all front joints ( driveshaft and axle shaft).

I actually replaced my front axle u-joints at the same time I did the locker. The u-joints are good.
The front driveshaft does not have any wiggle to it

Littlex, you said if the chain is loose enought to slip I have other problems. Spline damage on the front output shaft problems?

Is there any way to check the Tcase chain for slippage without taking the Tcase apart?
If I shift into 4WD and manually try to turn the front driveshaft, it shouldn't rotate at all, right?

Cheg,
The chain doesn't really slip if it's loose - what that noise is the chain catching on probably the shift node fork.
When I strecthed my chain I had chunks chewed out of the fork. Also had slap marks around the casing.
It really sounded like someone had a rubber mallet and was bashing the t/case when in 4wd....if this is consistent with what you are hearing....
Yes it will only occur in 4wd (hi or low).

Hey Wooders
Did you notice any loss of power when the chain slip was happening? I don't notice any, but I guess that's because the rear wheels keep me going.
A mallet hitting my Tcase? More like a sledge:eek:

There shouldn't be any loss of power because luike wooders said before...the chain isn't actually slipping...the slack in the case is just slapping around:rolleyes:

Ok Cheg, I'm now 110% certain that it is the chain based on your last bit of info (the sledge comment).

& as Supergper said its your t/case not your engine so it has nothing to do with power :rolleyes: ....

"Nothing to do with power"
I believe the Tcase tranfers power to the front axle and therefore has to do with power.
Don't mind me, I'm just being a smart-ass:flipoff2:

So, is there a way to check the chain for slippage (slappage?) :flipoff2: without tearing the Tcase apart?

Jezz next you'll want us to fix the darn thing for you.
If you REALLY must prove it, drop the front driveshaft - And go for a spin in 4wd - even though you front diff is discoed I bet you still get the noise.

BTW have you don a SYE yet? If not now is the ideal time.

"Jezz next you'll want us to fix the darn thing for you. "
Yes! You drink beer?

Well, don't I feel stupid:rasta: Good suggestion Wooders, I'll disco the front DS and if it still clunks in 4WD it is the Tcase. If it doesen't clunk then I move on to the front axle.

Just one question, with the DS discoed, will there be enough load on the chain to cause slappage?

If you have a stock 30 in your YJ with a front locker, your front driveshaft will spin always, even in 2-hi (i used to have a jy with that setup). And since you're not hearing any noises in 2-hi, i think that your problem is t-case related only. Can you feel the clunks in your shifter handle? And it'll only take you 20 min to yank the t-case, and another 20 to tear into it. I'm sure you've done it before, or can get someone to help you. take care of that chain before it causes you problems in 2-hi.

Did you by any chance add gear oil instead of ATF to the transfer case:question: If you did that will stretch the chain. Also, does the popping happen when you drive it in 4wd in a straight line? or only when you turn?

In a straight line, but especially when I turn. Why?

While out on a run, (or even in my parts store) I've had people with this similar problem. Theirs was the tranny mount loose slapping around. Especially in corners or on a side hill? Woldn't hurt to chech the Tranny mount, and any possible tranny or driveshaft contact with the cross member or exhaust shield,
(JUST A THOUGHT):usa: :smokin:

I've had my tranny mounts go bad and replaced already. And tranny "clunks" happen regardless of 2WD or 4WD since it doesn't take much torque to twist the tranny with bad mounts. My current clunking problem only happens in 4WD.

I disconnected the front DS and drove in 4WD. No clunking

Got a new chain for the NP231 and will install this saturday/sunday. From the posts above and my own understanding, I believe the TC is the source. Hopefully a new chain is all I need and the output shaft/bearings are OK.

I believe the chain is stretched. And I believe a phenomenom know as "chain suck" may be the offending noise source . As the chain moves around the drive sprocket it wraps around too much then suddenly releases with a loud clunk

Will keep this thread going until I solve the problem

This is to follow up on the clunking noise

Well I tore apart the NP231 and discovered marks on the inside of the case that was consistent with chain marks left behind by a stretched out and sucking chain. Also found a good helping of small metal chunks on the magnet at the bottom of the case. No gear teeth were broken so I stuck a new chain in and put the TC together

No more clunking in 4WD on the test drive

THanks all and especially Wooders and WideJ