went to remove my tcase drop and everything was fine, new bolts were in crossmember was bolted up. Went to drive and started geting a knock coming from the front axle. The knock sounds like a rotational knock, for example: everytime the tire does a full rotation I get one knock. I had someone drive It slow while I looked under and everything seems to be clearing (IE: front ds, rear ds, bolts, transfer case). So I put the 1" tcase drop back in and the knock went away? Im stooped...I talked to some guys on NAXJA and they say It could be the exhaust, or a tranny mount, but most likely the exhaust.
This were some of their replies:
QuoteIll bet its part of your exhaust banging on the underside of your Jeep....when you removed the TC drop, it moved your exhaust up a little too....if you had hit it before and already pushed it up, raising the TC back up probably put it even closer. Id check that first.
QuoteMy bet is on the exhuast as well. The torque of the motor will move it when selecting forward or reverse and removing the drop lifts it up an 1" closer to the floor.
QuoteProbably a worn tranny mount. I had the same problem/noise when my tranny mount was worn and the tcase was moving up and down with the revs.
QuoteWhile i cant give you an exact explanation, it just does...take a look at exhaust when someone takes off from a dead stop....they usually bounce up and down or go side to side a little bit due to the torque of the motor twisting the exhaust, etc. If its close, its thumping on you undercarage somewhere causing a knocking sound...took me a month and several hours under my XJ to figure out what the heck that noise was. Mine was most pronouced upon heavy acceleration in forward or reverse.
Like Kejtar said about the exhaust. Especially if you have the coffe can (round) cat converter. Basically all the pressure on the driveline makes it vibrate hitting the x-member. Im running a 6* shim as well but that says nothing. You need to look and see where your pinion sits too. I would proably count out the tranny mount if it only does it with the drop out.
Anyway thats what they had to say but I really dont understand why I could get that sound from the exhaust rubbing? It aint that big of a deal to lose 1" ground clearance but I'd rather have It out If I dont need It. Any thoughts?