Drivetrain noob seeks advice.

Yes I searched, yes I'm a noob, please help if you know anything about the topic
1989 XJ Laredo, 4.0L, AX-15, NP231, Dana 30/35. Hopefully that will help. I get a clunking everytime I either get into gear too hard or press/ let off the gas with any speed. I also feel drivetrain vibes at 45+ mph. Tires are balanced and vibe is majorly affected by gas/clutch pedal. If I drive perfectly with super gradual acceleration sometimes I can avoid the clunking. In neutral the motor doesn't twist with throttle so I don't think motor mounts are the issue. I haven't been able to team up with anyone to try looking under while they're operating. Checked out the tranny mount, seemed fine and tight, same with crossmember but I noticed while underneath I can wiggle my rear drive shaft side to side at both the front and rear ujoint. Able to move enough to make a metal clunk sound. Is this normal, should there be play in ujoints? I'm able to shift it side to side approximately 1/8th inch and can see greased innards where the needle bearings should be. I have video of shaking by hand I will post a link when I'm home. I think this is likely my vibe problem but can't afford replacing parts that don't need replacing. Any thoughts? Anyone think this could also be my clunking noise?

should not be noticeable play in u-joints. I would start by replacing those and then seeing where you're at. If you can shift it 1/8" and can reproduce clunk you definitely need to replace them even if that isn't the whole problem.

I will be replacing tomorrow, I figured it wasn't normal but have nothing to compare it with so I wanted to make sure. If anyone has any input as to some other common issues the XJ has that could be causing this please feel free to chip in =). If I've learned one things about Jeeps it's that there is always more wrong with it than meets the eye haha. After fixing these U-Joints I will likely notice something else haha. :fuse:

First thing I would do is get rid of the factory motor mounts and checked the trans mount thoroughly. Sometime they look good but can be split all the way through. U joint seems to be your problem though.

From that description it is not safe to drive it!!! Park it and change those U-joints NOW before you do anything. If the front one gives out while driving it can lift and jack-knife the jeep as the U-joint desintigrates!!!

Entire description is classic SHOT, past their end of life U-joints. I had one fall apart at 55 MPH on the free way once (when I was too young to know better, LOL), and it had all your symtoms. I was lucky it was the rear one that gave out. I have the same problem many times ever since, and was always bad u-joints. 1/8" play should be ZERO!!!!

While you're under there poking around, take a gander and see if the motor mount brackets on the engine have loose or broken bolts. Only takes a minute to check.

Thanks all, fortunately it was the rear than was going bad but the fronts I'm sure could use replacing. No play in them yet though. I visually checked the motor mounts and tranny mount and didn't find any problems. Got the U-Joints I ordered this afternoon and replaced. Whole project only took me an hour without snap ring pliers OR a U-Joint press and I have NEVER done a U-Joint before. Was semi-proud lol, although I'm sure someone will trump this with tales of them doing it in a wheelchair in 6 minutes or less haha. High speed vibration went away, as did the clunking with torque. 2 birds, 1 stone. :rof:

I have not tried the wheelchair yet, maybe soon, but hopefully not too soon:shiver:!!!! LOL