So I am rebuilding a GM 10 bolt out of a 1991 Trans Am. Its a 7.625 Ring gear.

I have kept the original gears, but installed new carrier bearings, and pinion bearings. The pinion pre-load is set and the priginal pinion depth shim was used since the gears were not changed.

Now here is the problem... I have to "pre-load" the Carrier with shims which also set the backlash. These shims are originaly one piece cast iron and you can not re-use them (trust me I tried and one broke). One was .240" and the other was .242".The replacements now come from Gm in two pieces. a .170" spacer for each side then you order shims that you need.

So I got the spacers and I tired fitting in some spare shims I had laying around and I cant even get close to the original specs. The case is just too tight. I think the closest I have come to the overall specs is .08"

So my question to you all is how do I know how much pre-load the carrier should have and how Do I test carrier pre-load?


Edit: I have an all-data account but the information on this subject is touchy at best and is not understandable.

The way I do it is like this. I start with the left side and add shims until the backlash feels about right while pushing on the right side race with a screwdriver to hold it tight. Then I come up with a shim pack that fits tight on the right side. It should be tight enough that you have to tap it in with a small hammer, but not tight enough that you damage the shim or housing while driving it in. If you can pull the differential out by hand then it isn't tight enough. Check the backlash and then make adjustments so that the backlash is correct. Always check the backlash with the bearing caps installed and tight. You don't have to torque the bolts, but be sure that they are tight enough to hold everything in place.