as i start the jeep there is a thump from underside of the driver seat. sounds like the strarter jumping around or trans? how do i see if something is loose? oh, and it doesn't always do it. but i haven't found a theme as of yet.

ideas fellas?

 

nothing? ok then. i'll crawl under there this weekend and see if the starter is loose or if the tranny mounts are loose. but if anyone has any ideas of could cause a thump underside
right when i start her up...

 

This is a tough one? Mounts would be my first guess, my second...a cat in the flywheel.

 

I'd have to say mounts, a cat in the flywheel sounds more like, "SCREEEEEAAAHHH THUNK THUNK THUNK" then starts to smell like burning fur.

 

X2 on mounts, mine was doing it at start up and shut down and it was motor and trans mounts worn out.

 

check your muffler system over make sure its tight and not loose where it could be shakin against your floor boards

 

I realize this is an older thread, did you happen to figure out the problem?

if not...
My heep likes to make a thumping noise on startup and shutdown where I believe the very last hanger on the exhaust (connected to the frame via a solid bar with a bushing inside) allows the pipe to rattle up and down, it seems to vibrate on moderate throttle up hills also (at first I thought it was gear noise). I have seen people just hack off the exhaust before this bracket to fix this problem...

 

Mount. Prolly drivers side. Maybe downpipe thumping CA"s or floorboards.