GM 12-Bolt Rear End Rebuild - Asphault Marker

Now the caps, which are a machined piece, need to go back on their appropriate sides. Steve had marked the caps before tear down so he knew which one went where. These caps are just a cast-iron piece of metal so they are the weak links in our rearend. If we wanted this rear to be a full competition unit, we would need to upgrade these. We'll use a killer aluminum cover to add some support to the factory caps because this rear will be in a street car.

Now Steve can check the wear pattern to see if all the shims are correct. After applying marking compound Steve rotated the ring gear by hand. As it meshes with the pinion the marking compound is removed and the wear pattern reveals itself. This pattern is too close to the toe or outside of the ring gear.

Steve removed the differential and the pinion so he could add one small shim between the pinion and bearing we mentioned earlier.

The idea is to get the wear pattern centered between the heel (bottom) and toe (top) on both the drive side and the coast side. If this is not correct, you could end up with a very noisy (whining) rear.

With the wear pattern centered, Steve slipped in the new axles, installed the C-clip, and put in the spacer. Unlike the factory, which uses a long pin to keep the axles pushed out to keep the C-clips engaged, the Truetrac uses this round spacer.

To help support our cast bearing caps, we installed this awesome-looking cover from Moser. The covers are made of 356-T6 aluminum and feature two support bolts that tighten up against the caps. This is designed to add support to the caps to reduce the amount of ring gear deflection making the gears last longer.

With that, the rearend was ready. We will fill it with this 85W-140 gear oil once it is installed in the car so we can set the fluid level properly. Because the Truetrac is a helical gear-type limited slip, it will not need a friction modifier to work properly.