Need Help w/8.75 Gear Swap

First off, do yourself a favor and buy a crush sleeve eliminator /shim kit.. They are $30.

I'm in the middle of doing my first 8 3/4 as well.

You can use you old bearing as a 'set-up' bearing after honing the inner race for a snug slip fit. That way you can make pinion depth shim changes easily. Once you get the pinion depth to where it leaves you with a good contact pattern, press the new bearing on. What I do is heat the bearing up and put the pinion in the freezer. Get a piece of pipe the same diameter as the inner race of the bearing and plop it on. The warm bearing expands a little and makes it easier for a do-it-yourselfer. It's about a .003 interference fit, so a press is ideal. I would not try to use a 3 jaw puller. You'll mess up the bearing if it grabs on the cage and not the inner race.

And yes, the outer bearing is a snug press fit by drawing it on with the pinion nut and and impact. Dr. Diff told me the torque for a 489 case with fine spline is 280 ft/lbs. So hit it with your impact until you get the right preload. If using shims/spacer, .001 spacer is about 5 in/lbs of preload torque. He said most people don't torque them enough during preassembly and when they assemble them, they torque them to spec and it changes the preload.

Once you've got everything set, take the yoke off and install the seal and locktight the new pinion nut.

Don't forget to lube everything with 80/90 when doing the mockup. It protects the bearings.

Also, don't forget to preload the carrier bearings also. Put white grease on the adjusters and just snug the caps down when doing the pre-assembly. Everytime you assemble and disassemble, things will change because the bearing will seat a little so be patient. It's a trial and error thing. Make Pinion depth changes .003" at a time and start with .036".

This is all info given to me by Cass (Dr. Diff).