[marty matthews]

I need some help identifying what I think is a pontiac rear axle housing. I haven't cleaned it up yet, so the only numbers I found are 9799100, and J 15 1 I think there is supposed to be a letter code on one of the axle tubes, but I haven't found it yet- too much road grime at the moment. Anyone have any idea what this thing is out of? Thanks!

[Tom Vaught]

Measure across the flanges where the wheels mount and the flanges where the brake backing plates would mount. That would help out a lot.

Tom Vaught

[Dick Boneske]

With the 979 prefix and the date code, I'd say it's a 1972 Pontiac axle manufactured December 15, 1971.

[marty matthews]

Thanks, I will clean it up a little, and see what other numbers I can find.

[John V.]

9799100 was the p/n for the center casting used in the '70-'72 Pontiac A body Rear Axle Tubes & Diff Housing Assembly.

I would decode J151 as October 15, 1971 as the date the part was cast.

Since '72 model year production had started by then, would indicate it was originally installed in a '72 Pontiac A body. The stamped axle code would tell you whether it was assembled with open diff or locking diff and what gear ratio. Of course, you could learn all that by removing the cover.

I'm not aware of any other usage for that casting, however some earlier Pontiac produced center castings were used in rear axle assemblies for other GM Divs. (in particular Olds), so not necessarily Pontiac only. The Manifest Code stamping on the axle tube would confirm if it was a Pontiac specific assembly.

[marty matthews]

Thanks John, and to all the others!