I have noticed lately that when i am stopped at a light (or wherever) with my foot on the brakes, I get a grinding sound coming from the rear end. It only happens from time to time.

1997 Jeep XJ Sport 4.0 Automatic. You can the full specs on my vehicle over there to the left under my user name.

Any thoughts on what is causing that sound?

 

In gear or not? Exhaust rattling? Monsters in the trunk?

 

It is an automatic, so yes it is in gear. Exhaust is not rattling and my particular cherokee does not have a trunk for my monsters.