Mystery Noise

I have a stock 2003 Jeep Grand Cherokee Laredo with a 4.0 and 151k miles. For a few years, I've had an intermittent noise in what sounds like (from the driver's seat) the rear right of the vehicle.

It is triggered by hitting a bump - even just a highway reflector on the center line - and seems occur more frequently when the weather is cool, damp, or humid (but not raining). It rarely happens when the car is warm, and it usually stops happening after I've been driving for a while.

The sound resembles grinding, almost as if you miss a gear (but it's in the rear and the transmission is automatic). When I apply the brakes as the Jeep is making the noise, it changes the tone of the noise (it dampens the noise like putting a pillow over a speaker), but it doesn't slow down or stop as a result of the brakes being applied.

I have had this checked out by a few trusted mechanics, but the noise is so infrequent that they rarely ever get a chance to hear it. I had a friend who is the shop foreman at a dealership (and a great mechanic all around) inspect the rear suspension, axel, and other external components in the rear of the vehicle, but couldn't see anything that seemed out of sorts.

Anyone have any thoughts?

 

intermittent problems never act up at the shop.... there are no lights for ABS, brake, or CEL?

OK the rear diff, gotta start somewhere - have you changed the fluid?
The WJ jeep has a weird upper control arm ball joint and all - often overlooked AND your description of after a bump, bounce on the road might be a placed to check...

GTG