3.9 diff gear install
 

Im pretty sure a few on here have done this. Ive done some reading on general guidelines for setting the pinion depth, checking the gear pattern, bearing preload, and getting backlash correct. However, if anyone out there has done this before, did you run into any snags, make any misakes, etc, that might make this go a bit smoother when I do it? Can I keep the old bearings? Do I need to buy a set of shims?