2000 XJ Sport, 4.0, Automatic, 4x4

It's done this since I bought it. Never gets any worse or any better. Only happens when I'm stopped, in gear, and goes away when I accelerate.

It sounds almost like a small, hard plastic ball bouncing around in a really confined space. The lower the engine RPM (the more vibration), the more frequent the rattling.

Anything common?

 

loose heat sheild,cat brooke down inside, muffler fell apart inside ...just a few thing to check first

 

Muffler is new, cat is solid, no loose heat shield. It doesn't sound at all like metal. It sounds like hard plastic (which I suppose could also be a bolt or something), but it sounds nothing like sheet metal or thin metal of any kind rattling. It's more of a rapid clunking, I guess.

 

Ever figure it out? My xj does the same thing but only started once I replaced the trans mount ?!?

 

i had an issue like that once. come to find out it was the exhaust rubbing up against the transfer case cross member. Not saying its what you guys got going on, but just a thought. i just used a jack and placed it under my exhaust near the cross member and jacked up all the way. was just enough to bend the pipe from rubbing. hope it helps.

 

It stopped doing it after the lift kit... never found exactly what was causing it.