The differential should have gear lube (GL5) in it, not grease. As far as the thump, make sure you don't have a broken engine or trans mount. With your foot firmly on the brake and the hood up, place the car in drive and slowly push the gas. Do the same in reverse. I the engine lifts on one side of the other, there is a broken motor mount. The trans mount needs checked from under the car. Also, make sure there isn't excessive play at both ends of the drive shaft (u-joints).
Let me know what you find.
Friday, January 9th, 2009 AT 10:58 PM