I have a 99 Cherokee 4.0 5 speed with 140,000 miles on it. There is a rumble noise in the rear around 37 mph, then at 59, and 71mph. I feel no vibration, but it is a bassy harmonic rumble. It does not matter if I am accelerating, backing off the throttle, what gear, or even if I am in neutral. I would normally think its the tires, but I feel zero vibration. Has anyone ran into this? Would you guess tires, wheel bearing, or rear diff problems. Rear diff fluid is full with no leaks or whines. Thanks.

 

I installed my 4.5 lift yesterday and noticed a simlar sound, but its only at higher speeds when I let off the gas and when i press it. Mine sounds like a grumbling noise. Its kinda deep, but sounds like a 1-2 sec deep grumble and I know for sure mine is coming from the back end.

 

At 140K it could def. be a carrier or pinion bearing in the rear diff.

 

Also, U-Joints and axle bearings. Could also be Tires.

 

I jacked it up and wiggled the u joint when I got it and there is no play in the rear end or ujoints but there is play somewhere inside the transfer case. The jeep is all stock btw.

 

Last month i noticed a sound similar to what you described coming from my rear end particularily the passenger side. come to find out at my next tire rotation i had two jammed wheel bearings. Big-O tires replaced them for free which amazed me. good luck

 

Check to make sure exhaust is not rubbing anything.