Rear end ID Help for 1966 GTO

[REED]

Hello Pontiac Community!  I have a  66 GTO and ordered a direct replacement axle shaft and found out that my rear end had most likely been replaced and the axle did not fit.   I  have a 10 bolt GM 8.2 inch BOP rear end that is a non C clip.  It does have a torsion bar and I read that was not available until 1970.  I'm  trying to  find out what rear end I have so that I can order a new axle shaft.  Any help from the community is appreciated.

Casting numbers on the rear end are 9793235 with  a 5 1 above it.  I was  unable  to find any other markings on the axle housing  as it's  been heavily painted.  Thank you for taking a look!

Reed

[Ringo64]

I don’t have any info but just wanted to welcome you!

[Frosty]

Hi Reed,

Let's start with the 4 character casting date of the diff. That would be located at the top of the pumpkin on the driver's side, as shown below. That will tell us what model year diff we are dealing with. It is not unheard of for guys to install C-clip eliminator kits to go racing as a lot tracks and sanctioning bodies have rules against C-clip diffs. That said, let's start there.