My dad is giving me his '90 XJ, and I've been driving it for a while. I've noticed a few things, one of them is a clicking sound. It is discernable but not noticeable when not in gear, but in gear it's annoying. The shop my dad took it to didn't notice it somehow, but everyone who rides with me asks me what it is. It sounds like a light rubbing, and it changes in frequency and loudness with engine rotation. The same shop replaced the engine about a year ago, but I don't know if the clicking started then. I probably can't do anything about it for quite some time, but I'd like to have an idea about what it would take to correct.

auto or manual?

Auto.

wierd perhaps a stator suport bushing is messed up.

you said it goes with engine sound? will it make it in drive, but not moving?

I just went out and tested it. The loudness is proportionate to the torque and the frequency is proportionate to the speed of the engine. I made a video with my digicam, but I can't hear it, so I'll take my laptop out and try to record it with a dynamic mic.

it really sounds like a bearing/bushing is starting to give out...

cracked flywheel

GreyScar has my vote!! When the flywheel(flexplate) begins to crack, it will make a sound like you are describing. The way to confitm this is to remove the inspection cover underneath, and while the engine is running, spray some lube at the flexplate. If it is cracked, the noise should almost disappear. While you are down there, it is always a good idea to check the converter fasteners for tightness.(WITH THE ENGINE OFF!!!) Good luck...Mike <img src="/forums/images/graemlins/oink.gif" alt="" />

Would that also cause the engine to make make a high-pitch hum and the truck to vibrate at ~4000+ revs?

4000+ ? Are you kidding PLUS? Sure it vibrates! It is near coming apart. You will vibrate too just before coming apart.
BJ