Drivetrain Vibes, With NO lift?

I have an 89' XJ Limited with np242, AW4, Inline 6. It has 191+ on it today. I was driving home yesterday, when i noticed it acting weird. This was in heavy rain, and i was in full time. Whenever the gas is released and then put back on, it clunks. It seems as if in-and-out of gear. It also vibes a noticeable bit. It gets worse when in 2wd. I'm thinking its a combo of the aw4 and diffy's. Would changing the fluid help this? I have no idea last time it was done, i know its a good idea, but with no job, it will cost too much. Does anyone know what i should look for? I was thinking of checking the steering just in case, i had the tire-rods done recently. I have acces to alot of tools at school, and a hydraulic lift. Any direction is appreciated.

Thanks, Justin

Check the driveshaft u-joints. Id be surprised if its your rear end, feel the pinion for wobble and pop the cover to do a visual. Its very unlikely to be an internal transmission issue. You might check your engine, tranny, and t-case mounts if all else fails.

Will do tommorow, Thanks

Justin

2nd on the u-joints. Does your tranny clunk when you put it into drive or reverse?

Another REMOTE possibility is that you may have a crack in one of your wheels. I spent months trying to track down a strange driveline vibe on my XJ and it ended up that I had some hairline cracks on my aluminium wheels.

Yeah i will check the U-joints today, and my tranny does clunk.. Sometimes harder then others.. Thanks

Justin

Check u-joints first, then output shaft bearing on XC if the joints are good.