Olds 9.3" 12 bolt or is it

[chevy56]

Hi,

I do not know much about Oldsmobile differentials but I was lucky and found this forum of experts. I have a few questions about the differential I have in my Chevy!!! The previous owner built this, do not blame me

According to him the differential is from full size Oldsmobile and has a 2.73 gear ratio and posi (both tires get hot during burnout). Sorry for my bad quality photo, it looks like an Oldsmobile 9.3 12 bolt 65->. And how about axle flanges, are these from Olds or aftermarket? The axle is narrowed so at some point there has been cutting and welding. I know this is not a lot of info, but is it possible to find out more details? The plan is to change bearings, seals, gasket, and get disc brake caliper brackets to fit axle flanges. Thanks a lot.

[monzaz]

Yep, Oldsmobile Full size car rear 1965-1976
So the only way to know which era 65-70 or 71-76 is the pinion spline
30 spline pinion is 1971 - 1976
28 pinion spline is 1965-1970 era

Both are 31 spline axles BOLT IN STYLE

65-70 era has 30 degree cut spline 31 spline
71-76 edra has 45 degree cut axle spline 31 spline

Housing end does appear to be the OLDER 57-64 era ends WHICH could be the same as 65-76 era too.
going to taker the large Ford 9" bearing 3.150" diameter
part number 514003P for the bearing 51098 for the seal (or could be 8940s in the olds)
That is what we got - hope it helps some. Jim
JD Race

[monzaz]

here are the dimensions of the olds pontiac flange end to see if they match yours. WHICH is does look like to me. Jim

[chevy56]

Jim, this is great information and helps me start my project. Thanks!

[monzaz]

Ok if you have anything else send some pics will try to help.
Jim