Originally Posted by artwork

Here is my process that I follow...

Diff building tips:
1) Clean hands and have a nice clean flat surface to work on.

2) Sand the diff rings on both sides with 600 grit wet dry sand paper. (Figure eight pattern seems to be the best). Take your time here seems like the diff rings need lots of TLC to get them flat and even. I use an old diff half for this part or you will burn a hole in your finger (this from personal experience). Motor spray on the sandpaper and then start your figure eight pattern. Add motor spray as needed. Clean rings with motor spray once sanding is complete.

3) Clean the 3mm diff balls with motor spray and set a side for now.

4)Gather and clean eight thrust balls and the thrust washers. Put the first washer on the diff screw and put a good amount of black AE grease on the washer. Put all eight thrust balls in the grease and then put the other washer on top of the thrust balls. Insert into the small diff half. Set aside.

5)Install the washer, diff ring, spring, bearing, and t-nut into the large diff half. Coat the diff ring with a small amount of silicone grease and rub it in (the clear grease). Set aside.

6)Take the small diff half and install the bearing on top. Install the diff ring and coat with a small amount of silicone grease and rub it in. Install the pulley. Take the clean diff balls on a clean paper towel and squirt some silicone grease on them. rub in the grease so that all of the balls are coated. Insert each diff ball onto the pulley (I use a small tool to do this, they seem to stick pretty easily due to the grease).

7) Diff is now ready to assemble. Take each half and put them together and start to screw in the diff screw. Once it starts to catch tighten until the pulley can't still rotate while holding each diff half. Then back it off one full turn. The diff is now ready to break in.

8)Diff break-in...Turn on your car and put the right side tires (left side should be off the surface) on the bench and then very slowly pull the trigger. Let the tires spin for 15-20 seconds and then stop. Let the car cool off for a few minutes then do the other side. After the car cools again tighten the diff a half turn and then repeat. Repeat this process until the diff is just tight enough for your racing application.

Some added info:
Slight grooves in the diff rings are a good thing, but should not get too deep. Sanding the rings is a really important step that cannot get skipped every time you rebuild your diff.

Hope this helps!