I could definetly use some insight/suggestions tonight.

We attempted to put a posi in my nonposi rearend. I used Jordan Musser's writeup and things were going swell. Then i kicked the pan that had the shims for left and right side seperated. So those got mixed up. Then as we were putting the diff in and hammering the shim into place it decided to break in half. Not a good thing. So now i have some questions.

1. Are the left/right shims the same? How imperetive is it that they are in the proper side?

2. Where can I obtain a new shim? Autoparts stores couldn't help me.

3. How do you put the diff in without breaking another shim? Is there some special trick or was my old shim just old and weak?

4 (and final) What holds the c-clips in once reinstalled?

Thank you very much for any help!!!!!!

 

You shouldnt have to hammer the shims in. You should put the thick shims in, then the differential. Torque down the main caps and check backlash. Add/remove shims as necessary to obtain your proper backlash. The shims should be snug, but not tight.

 

I personally watched a friend of mine install gears in the rear of my car (has many years of experience with drivetrains). At the most you should just have to work the carrier in the housing with your hands where it's very snug. If you have to hammer it in then you need to find some different size shims. He already had a massive collection of shims in his shop so i can't direct you where to get more, sorry. With trial and error he was able to get the shims needed to set the correct depth on the ring gear, but never had to hammer on anything. Not sure about your carrier, but on mine the shim on the driver's side was thicker than the other one.

While you're at it i would suggest getting a solid pinion spacer with shims instead of the crush sleeve. My buddy told me that the main reason the 10-bolts fail is because the crush sleeve isn't strong enough to resist the compressive forces that the gears make when you hammer on it. The plane on the gears makes the pinion have a tendency to want to shoot out of the rear towards the tranny. The crush sleeve is set by "crushing" it to the correct depth... so when you start making a good deal more power than stock it tends to get crushed more. When it's crushed more you lose the original contact patch and then you start breaking teeth. I bet this is one trick the guys in the 10s on the stock rear use to make it live (along with studs, girdles, etc). HTHs

 

If the shims aren't tight then preload on the carrier bearings is not there. They make a shim driver tool, or you can make one out of wood. I took a 3" x 1" about 8" long and cut a half moon into one end. It works like a charm. Cast iron doesn't like a hardend steel hammer thats why it broke.

In most cases if the shims are in backwards the diff will not rotate. So measure the one you brokw with a good caliper and get a replacement from GM.

I always install the diff with one shim already in. Then I lightly drive the other in with my awesome tool. I have done 6 this way so far.