3906 diff

[JERRY2KONE]

Lito hit it right on the head. Your pinion gear was not shimmed in correctly to increase the contact area between the two gears. Plus are you using plastic casings? That can also give you flex in your diff which will cause early wear on your gears. Most of the guys in here run the 1/8 scale gears in their setups just because they are made heavier, stronger, and seem to be better machined in general. Still you can make the stock type gears work if you shim them correctly. There have been plenty of threads posted eluding to this fact and showing exactly how to do this.