I have a 99 XJ that when fully warmed up and I come to a stop I get a thump in the front end. Then if I suddenly accelerate another thump. It actually feels like something rotating. It doesent do it when cold I can drive it as hard as I want and nothing. If I slowly accelerate its not noticeable. If I am turning not noticeable. I have look underneath it looks ok. I even wondered if it could be a tranny problem. Any ideas. Thanks

 

motor mounts?

 

Motor mounts check ok.

 

how about your U-Joints or CV joints (which ever your jeep has) also check ur ball joints. these may cause it but im not a mechanic just ideas

 

slop in some bushings somewhere? tranny mounts?

 

its not noticeable till very warmed up. it does feel like the trans is moveing or shifting under my feet and seat. tranny mount does look ok but i can move it or stretch some when cold.

 

Grab the drive shaft and shake it in every direction. Check the exhaust tail pipe aswell.

 

I have the same thing in my jeep, mine is coming from the rear end and i am 99% sure that it is axle rap, my springs are worn out pretty bad and i believe that when i stop my rear axle is actually moving slightly to cause a thump. This only happens when i stop harder than i normally do.

Just an idea and something for you to look at.

 

Yes it does feel like an axle rotating. I feel it beneath the seat in floor. I originally thought it was front but I do feel it more under my seat.

 

ill get a picture of mine tonight if i can, i think last time i was under it if you looked really closely you can see where the mount is rubbing on the axle. My leaf springs are really really bad, they are just about flat. Im just waiting till i get some time to install a 4.5 lift from rustys to fix the problem.

-dave

 

Does yours do it all the time. Mine is fine untill fully warm or driven for 10-15 minutes.

 

to be completely honest i haven't really payed attention to that part of it. I will let you know after i leave work today if it will do it right off the bat.

 

i have confirmed it does make that sound right away, however it is much much much quieter when the jeep is cold.

 

Thumping sound was dry spline on rear driveshaft slip yoke. Found write ups on this on other site. lubed splines so far no problem.

 

glad to see you got it fixed, could you post a link to the write up?