8 1/4 Gear Change Question

When I went to 3.55 gears in my 8.25 I got a master rebuild kit (all the bearings and seals) and ring/pinion from Randy's. It came with a video that was very good on the basics of rebuilding a rear end and setting up the gears.

I would recommend getting a setup pinion bearing too. It slides on and off the pinion and will allow easy changing of shims to get the pinion depth right.