Need Help Identifying GM 10 bolt rear-end.

[F1fanatic]

Hello-

I am resto-modding my 1968 Pontiac Firebird. Most everything in the car is stock except for a few odds and ends and the engine.

I am starting to service the rear end of my car and I am trying to identify what I have here. I believe it is an 8.5" 10 bolt because of the big square lugs at the bottom. But when I look at production years, from what I can figure, they only ran 8.5" rear ends on 70-81 GTO/Firebirds. I bought the car from the original owner back in 87.

Can anyone help confirm here? Thanks for any help.

[rchaskin]

The easiest way to id a 8.2" or 8.5" ten bolt is the pinion nut.

The 8.2" uses a 1-1/8" socket on the pinion nut.
The 8.5" uses a 1-1/4" socket on the pinion nut.

[F1fanatic]

Thanks for the quick reply. That sounds like a sure way. I was hoping I could come across a process that didn't involve taking the driveline apart at this point. I suppose if that's the only surefire way.

[BonzoHansen]

Thats an 8.5 i think

[F1fanatic]

I agree. I found this chart as well. It seems to indicate the same. Based on this chart it can really only be #17.