Ok so lately when I start the beast up I hear a thump under my seat area/middle of the Jeep. Im thinking its the Xfer case just from the location of the sound but that doesnt really make sense to me. And heres the thing it doesnt happen everytime! Its done it while its cold, already warm or maybe go a week before doing it....you think it has anything to do with how long I turn the key (cranking over)? Cuz I cant think of any good reason for what it is and I dont want something falling off on the freeway lol .....Help

 

My guess would be the exhaust pipe, or a shield hitting the floorboard when the engine cranks over.

 

I have a rotational sound near the middle under the console, I think it's the converter bolts hitting the inspection plate.

 

Check your transmission and motor mounts. if the transmission crossmember is bent the exhaust may be hitting it.

 

THUMP under seats during start-up is almost always the exhaust pipe hitting the transfercase crossmember.

There is very little room between the pipe and the crossmember to begin with.
Weak hangers, bad/misfitted exhaust and tired transfer case mounts don't help the situation.

Most aftermarket manifold pipes come with a hanger bracket on them, but I found they are basically useless.

I fixed several of the start-up thumps with a replacement exhaust hanger from RockAuto.
Called an Exhaust System Hanger.
WALKER #36412

RockAuto wants $14 for it.
(Use discount code 28481691136032 in "Where did you hear about us" field for an extra 5-10% off)


Its basically an exhaust clamp with a stout bracket welded to it. Not only does it hold the pipe UP but pulls it slightly to the driver's side making tons of room.

Only thing that will need to be done is to drill a 3/8" diameter hole in the RUBBER mount that is already on your XJ.
The opening is just a slot. Bracket can fit.

Just offering up this info as an option.
Flames are best left for classic hot rods.

 

Ya I was thinking mounts but Ill def check out the pipe too. I know I did bend the crossmember for the Xfer case last time I was out but not bad so that might be it