Hi, i have machined my posi-cones and case halves..
Now im goint to shim the posi to 0.
How do you guys measure it?

Do you always use the same amount of shims in both sides?

I mean it can be worn more in one side so that side needs more shimming right?

Thanks

 

I'm in the process of rebuilding a Borg Warner unit for a '66 GTO. It's the same design as the 9 bolt. I have machined the case and I'm ready to shim it. I'm going to put caly between the gears and the cones and assemble the case without putting the springs in it. Then I'm going to take it apart and measure the thickness of the clay to see how much it was compressed. I'm going to use shims that are about .005 thinner than the clay.

This is similar to the way some people check valve to piston clearance.

 

That might be a good way to measure it, i think. Have you checked if you have different measurements between the both sides?

 

Don't rely on both sides being the same. I put shims in until there was a tiny amount of rock in the spider gears then reduced the shimming in small stages until there was no movement. Has work perfectly for me so far.

 

It would be best to do one side at a time if you are checking the gears by rocking them. That way you can tell how much clearance you have on each side and adjust them so that they are as close to equal as you can get them. Also, if there is a lot of difference in the amount of shim that you need on each side you might try switching sides with the cones and see if it come out a little more even.

I'm going to be using hardened thrust washers in this Pontiac 8.2 differential. There seems to be enough slop in the axle splines that it's allowing the gear to move on the top of the cone, which is causing wear on the gear and cone where they touch. I'm worried that a standard shim might get chewed up and end up floating around in the oil as metal shavings.

 

ill go for the standard shim now, maybe ill get it good if i try adding/removing shimms until i get no play or just a tiny play.. its street driven so what i understood is that it should not be preload on them in street use.

 

Yes. I made sure I kept the cones, gears and shims always in the same orientation. I spread them all out in a line on one clean sheet and flipped the parts in place as needed. That way they were all in order for final assembly.

 

My brother did his a couple years ago. When we did it, we machined the gears taking note on how much we took off. We then reassembled it with the same amount of shims equal to the material taken off the cones (ie, took .100" off the cone, added .100" of shim).

 

You have to add in the amount of wear in the case (how far the cones sunk into the case).

 

Got a chance to work on the BW differential today. I couldn't find the clay that I used years ago to check valve to piston clearance, so I used the trial and error shim method. It's going to need .045 shim in both sides. I cut .100 out of the case so there would be plenty of room for more wear. I'm going to make some shims out of hardened spring steel. I've got another one of these to do a little later for another '66 GTO.