Clunking noise when under load or turning

[dberes]

So this started out on a trip we took last week - on the way home I noticed around 35 or 40mph and then accelerating, I would get a constant clunking sound. Took it to the stealer and he put it up on a lift, said the front Driveline was worn and loose - I replaced the front drive shaft with a new one, and while I was under there I dropped the transfer case (had a leak) - opened it up and found my shift fork was worn down. I cleaned up the case put in new fork - mounted everything back up and took it for a test drive. I still have the clunk sound, and if I put it in 4 LOW and turn real sharply at low speeds it clunks really hard (not one clunk but continuous). I've read other reports and it was anything from CV joints, Viscous Coupler, Drive shaft etc..If I drive straight and do not give any gas, no noise - once I accelerate I get the clunking until I let off the gas. So it only seems when any type of load is on the front tires, including a load when turning - does the continuous clunking occur. (2000 Grand Cherokee LTD, 45RHE Trans, NP247 Transfer case, 100k miles, quadra trac)

[dberes]

Update: While my son drove and did circles..very very slowly - hard turned to the right in 4LO I could see the Front Drive line binding and transfer case was clunking - I just redid transfer case and fork didn't see any other issues. It will do it in 4HI as well just not as extreme - and it does it under load - is it possible the chain is skipping? or is it a viscous coupler issue? Or is it even Transer case - what about front gears? The sound was not coming from CV, Trans, or Suspension - it was strictly isolate to front drive -line and transfer case connection. Any suggestions are appreciated - wife is giving me stink eye to get her jeep back.

[dberes]

Sorry..I said Viscous Coupling - which is on a 249 correct? I have the NP247 so it's a Progressive Coupling - as I understand it, if the PC was going out, I would just be in 2WD but no clunking - so if I drop the front drive shaft and try the turns again, if no noise is it Transfer case? if I still get noise, then something like Varilocks..can someone confirm

[lifted1994xj]

Not to familiar with the grand t-cases but i know you should never use 4lo on the street especially while doing circles that will tear it up in no time at all.

[dberes]

THanks Tommy - It was a very slow circle in my grass field to duplicate the clunk.
I also lifted all tires off the ground - in 4 low - let tires turn at their normal rotation - upon hitting brakes could hear transfer case clunk. I removed the front drive line and am completely unable to duplicate any noise. So it has to be with load on the front drive shaft to duplicate sound.

[lifted1994xj]

Oh ok i should of asked what kind of surface it makes the sound on, sounds like you are narrowing it down. Hope you are able to figure it out.

[dberes]

I don't know if I'm closer or not..lol...I'm back to square one..I wish someone else had this issue and can tell me what it is..chasing the issue is a pain - I just want to fix it and move on. So I'm too it either being something in transfer case (PC, Chain), or front gears. Questions if anyone knows the answers too:
1) If I take the front drive line off, I'm still turning front gears, but I don't get any noise, could it be gears if only under load or should I hear it all the time?
2) If it's in the transfer case, could a Progressive Coupler make that type of sound - from what I read if it fails, it doesn't clunk, it just fails to 2wd in the rear.
3) Is it possible the new drive line I bought is defective?

[ittray]

I would tear that t-case apart and check the chain. Also, have you thought about the front axle's pinion gear bearings? Sometimes when those get worn out I have seen the pinion gears move enough the cause a clunk. With the front drive shaft off, I would shake and pull on that front axle yoke to see if there is any play in it. Good luck

[dberes]

Thanks ittray - When I tore it apart last week - chain and gears looked good. How much play or lack of play should the chain have? Would the chain cause a clunk with a load on just the front end and not rear? Thanks for suggesting pinion gear - I did check outer CV joints - all looked good - but I haven't torn into the front axle gears - That was my next task - I appreciate the feedback any help is appreciated as I'm getting tired of being under there

[ittray]

Well, I am not totally sure how much slack there should be in the chain, but I would guess that if it were the chain slapping the inside of the t-case you would be able tell with the case apart. Are all of your mounts good? (engine mounts and t-case cross-member mounts)

[dberes]

Yep yep..after reading some forum info, they suggested that so I checked all mounts to make sure nothing was loose. I think you maybe right on the pinion gear - except I can't check that until back next week from business. I'm thinking the "clunk" is the after affect..such as gear binds up, you can see the drive line hesitant as if binding, then the clunk - so possibly gear hangs up the line and the slack builds in the chain, when the pressure releases the chain smacks the transfer case and makes the clunk..At least in theory it sounds good..

[ittray]

Originally Posted by dberes

Yep yep..after reading some forum info, they suggested that so I checked all mounts to make sure nothing was loose. I think you maybe right on the pinion gear - except I can't check that until back next week from business. I'm thinking the "clunk" is the after affect..such as gear binds up, you can see the drive line hesitant as if binding, then the clunk - so possibly gear hangs up the line and the slack builds in the chain, when the pressure releases the chain smacks the transfer case and makes the clunk..At least in theory it sounds good..

<- Makes ya kinda wanna do this huh? hahaha let us all know what it is when you figure it out.

[jeepgod]

I had one do this similarly to mine and it gradually got worse (I own XJ's now but had a few ZJ's also) It was the chain slipping and pooping when it was under a bind or load, it did this in 2wd too sometimes on pavement(that is how I found what it was by doing it on pavement to amplify the problem). When we took it apart, everything was fine in it and the chain didn't eat the casing or anything but we replaced the chain and sprokets and problem was solved.

Hope this helps.

[ittray]

Originally Posted by jeepgod

I had one do this similarly to mine and it gradually got worse (I own XJ's now but had a few ZJ's also) It was the chain slipping and pooping when it was under a bind or load, it did this in 2wd too sometimes on pavement(that is how I found what it was by doing it on pavement to amplify the problem). When we took it apart, everything was fine in it and the chain didn't eat the casing or anything but we replaced the chain and sprokets and problem was solved.

Hope this helps.

pooping? hahaha

[jeepgod]

Originally Posted by ittray

pooping? hahaha

OMG, that is too funny...the keys are soo close together...oops Well, one slip of the finger and it can get dirty