lol wow. thats pretty rare to happen unless u do alot of burnouts or put alot of abuse on that diff. take it apart check the ring gear for wear, i doubt its the ring gear but go ahead and check. i suspect its the pinion bearing, could be the front or rear pinion bearing but its not like it matters now, you might aswell change both. its a pricey fix at a shop, youll need to buy a rebuild kit for your diff, which will make sure that diff lasts another 150,000 miles. go to randysringandpinion.com or summitracing, and you can find it there, itll come with new bearings, shims, case bearings, axle bearings, oil seal, everything. now is also a good time to swap out some steeper gears if u want more performance out of your car