Vibration/Clunk when accelerating hard from a stop

posted about this before, but only response was u-joints, which didn't fix it. getting desperate!

01 XJ, auto, np231, 3" lift, 31" tires, 100k miles

Couple a weeks ago, when taking off fast from a stop, there was a vibration and then a clunk clunk for less than a second, coming from what seemed like the center tunnel. If you take off gently, it doesn't do it. Innitially the problem only happened when the jeep was loaded down, and quickly started to happen even when empty. Now problem can be felt in floor and pedals but can't isolate a location.

So far, I've changed all fluids. Changed driveshaft u-joints (and balanced shafts). A tranny shop dropped the pan on the tranny and didn't find anything "unusual", replaced fluid and filter. The transmission mount looks fine (no cracks, solid rubber still). There doesn't seem to by any abnormal play in the front or rear diff's as felt by turning the pinion with tires on the ground.

I really don't want to take this to dealership... so anything else I can check?

Thanks!
Kristoffer

I have on '01 and had the same problem. I replaced all the U joints a couple a weeks ago and put a nice coating of wheel bearing grease on the slip joint that comes out of the transfer case. That took care of all my "clunking" issues.

Had the same problem with my 92', seems when i dropped the transfer case to accomidate the lift vibes it broke the bracket on the exhaust at the crossmember. grab your exhaust at the cross member and give it a good shake.

XJMAN said:

I have on '01 and had the same problem. I replaced all the U joints a couple a weeks ago and put a nice coating of wheel bearing grease on the slip joint that comes out of the transfer case. That took care of all my "clunking" issues.

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already did all this, and yep, greased the slip joint up reall nice like!

jeepless said:

Had the same problem with my 92', seems when i dropped the transfer case to accomidate the lift vibes it broke the bracket on the exhaust at the crossmember. grab your exhaust at the cross member and give it a good shake.

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thanks, I'll check this

kristoffers said:

thanks, I'll check this

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no broken brakets, no movement in the drivetrain or exhaust or anything else that hangs off the body.

it really seems to be "inside" the drivetrain, it's almost a grinding as much as it is a vibration. what in the engine, tranny, or transfer case can grind/vibrate only under initial load of accelerating from a stop?