asuderma

Hey Guys,

I have 92 XJ with 207k miles on it, and I am noticing some strange things.

First, while I am driving, I hear a loud thunk/ping when I let off the gas and when I hit the gas again. Occasionally this happens while shifting to drive from park.

Second, from a stop, when I hit the gas, I frequently hear a grinding/groaning noise (not sure which it is, hard to tell). This sound goes away after a few seconds, and if I accelerate real slow I don't hear it. It never makes this noise except while acclerating from a stop.

Any suggestions you can give would be awesome, thanks.

ZINGGG

Check fluid levels, colors, smells.

Check ujoints for play/binding.

Check exhaust to make sure it isn't hitting the crossmember.

Check motor/trans mounts.

884x4

agreed with the motor and trans mount comment. maybe look at your radiator to see if the mechanical fan is touching the radiator(doubt it but never hurts to check) if it is then that's your motor mounts. maybe put the vehicle in park and have someone hold the brake and hit the gas to see if it does it or if your engine moves. check fluids and u joints. my exhaust was hitting my cross member but it was more of a tapping noise
anyway, goodluck man!

asuderma

Thanks for the advice so far. I know the exhaust is okay, I just replaced the muffler and didn't see anything out of the ordinary there. (Got rid of another noise I had been having forever though, huge hole in muffler on top).

I will check the mounts and fluid levels later tonight when I get home (been meaning to check fluids for a week now). I'm just really hoping it's one of these simpler solutions and not a problem with something major.

I will post back later when I have results

asuderma

Only managed to get time to check the fluid levels, and they are all good. I have been listening very closely, and I think that mounts may be the issue.

I will post when I find the time/place to check them.

Thanks

asuderma

I know it's been a while, but I crawled under there on Sunday. Finally managed to use a garage, since it's been pouring for a week in Denver. The front U-Joint on the rear driveshaft is toast. It must have had 1/4" of play in it. Going to replace that ASAP and see how my noises do.

Thanks for the help as always.

asuderma

Thought I would close this one by posting my final solutions. I ended up replacing both motor mounts and the transmission mount. The grinding sound was the fan on the shroud under acceleration. The wear was so minimal that I didn't notice it before, and it wasn't hitting the radiator like some do, just twisting and hitting the shroud.

Between all the mounts and the U-joint replacement, she runs a LOT quieter now.

TL;DR Replaced Motor and Transmission mounts and U-joint on driveshaft