differential question

[Yves Thaens]

Hi,

Someone restoring a 72 vette called me today with a question that I couldn't answer. Maybe someone can help.

He wanted to know what nominal pinion depth would be on a 3.73 rear end. He's rebuilding his differential.

Thanks

Yves

[Gary R.]

Re: differential question

Each gear set is matched and the pinion depth scribed on the end. You can't set the depth but using a depth mic or gause from the bearing pads surface, you need to have the reference point on the center line of the ring gear and need a tool that works off the carrier bearing bores.
I use the pattern method to set up new or used gears. You're better off starting with the pinin shim that was on there and using a setup bearing to dial it in. If you don't have the shim start with a .029" shim.

[Michael H.]

Re: differential question

Yves,

If your friend is refering to the selective pinion bearing shim thickness, there is, unfortunately, no way to determine this easily unless you have the proper tools that were designed to gauge the precise housing/bearing dimensions. This tool/dial indicator would automatically gauge the exact depth of the rear pinion bearing when installed in the housing and the shim thickness would be calculated from that reading.

If he is using the original pinion with a new bearing, I would guess that the dimension would be close to the original and it's possible the original shim could be used again. However, I would highly recommend using the information and pictures in the factory service manual to do a "pattern test" on the ring gear to insure that the depth is correct. New good quality bearings are typically within a few thousandths of the original but some do vary more than that.