63 Differential Yoke

[Joe S.]

I had my differential overhauled due to a cracked carrier. WHile at it, I had new pinion and ring gear put in. I found out when I picked up the diff that the pinion required a different yoke. The new yoke looks like a later model and is more beefy. It also sticks out about 1/4" more than the old one (shouldn't be a problem at the tranny end) but also just has a flat plate that fits up flush against the end of the housing. This differes from originals where they yoke has a cup that fits over the end of the housing and seats down in about a 1/4".

Mechanically this should be fine. However, is this going to create a deduction? I know the gears (other than in performance testing) and other parts of the carrier are not judged. Should I let it go?

Thanks again,

Joe..




Joe and Joanne's 63 FI Convertible

[Gene M.]

Re: 63 Differential Yoke

Joe, Relax most of the chassis judges will not have access to the pinion yoke to see the difference. A mirror used on a '63 in this area is very hard to see the diameter difference. And all doubt point wise is in favor of the car.

[Joe L.]

Re: 63 Differential Yoke

Joe-----

The reason for the need to change the pinion flange is that original 1963-64 Corvette differentials used a "coarse spline" pinion shaft. I don't think that anyone produces R&P gearsets for the 63-64 spline configuration anymore. GM ceased many years ago.

So, if the gears were to be replaced, then the 65-79 style pinion spline gearsets had to be used. These are the only ones currently manufactured by sources like Richmond Gear and U.S. Gear.

The change to the 65-79 style pinion spline also requires a change in the pinion (companion) flange. The flange configuration that you described is new to me. I've not seen a 65-79 pinion flange of that configuration. Essentially, the 65-79 pinion flange is configured like the 63-64. However, the 63-64 flange is unique in cross section and you will not find a 65+ style flange exactly like it. However, as I say, the 65+ style flange is more-or-less configured like the 63-64 and does have the cupped shaped deflector and fits to the housing just like the 63-64. The GM flange is GM #3878972 and is still available from GM for a current list price of $96.44. All I can figure, based upon your description, is that the flange you have is some sort of aftermarket piece.

[Joe S.]

Re: 63 Differential Yoke

As always, thanks for the info. I'm gonna talk to the shop. I don't want to get hung up on it but if we can make it better, so be it.

Appreciate the info.

Joe..