Replaced my cracked manifold...hoped the weird vibration noise would be solved.I can't hear it in the engine bay but when your in the Jeep you can hear it thru the floor.It's a fairly new Magnaflow exhaust...I was thinking the mount by the crossmember might be causing it...my buddy suggested a bad motor mount, but I don't see any excessive lurch when the motor is reved.

 

I think you may be right about the pipe. It may be resting on the crossmember. Mine did that and I found that the welded rod had snapped off the pipe. I welded-up a new, somewhat stouter replacement piece using some old rod stock. Found a clamp-on repair kit for the same thing about a week later...

 

Oh yeah! My system is a MagnaFlow also. The tailpipe after the muffler was resting against the top of the passenger side rear shock absorber. Of course I didn't see this during installation because the rear axle was dangling then. The geometry changed after putting it back down on the ground.

 

So...I guess I should pull out the creeper.Did you have the floor vibration issue too? First I thought it was the cat rumbling but the noise is actually more noticeable in the interior.

 

I have a vibration inside my catalytic converter. It was loud until I got my engine running smooth.

 

I had a vibration on my xj, turned out one of the rubber hangers has holes that are large enough to allow the metal hook to vibrate in the hole. I found out by laying under the jeep and pushing up on the exhaust and the vibration stopped. When the weather gets warmer I'll replace the hangers.