How can you tell a three series posi case from a two series posi case when looking at them on the bench? I have both 10 and 12 bolt units but I am not sure how to ID the series.

If you can see the casting #, that'll help.

For the 8.5" 10 bolt
410408N is the 3 series, and 410409N is the 2 series.

The other alternative is to count the gear teeth, then look here:
http://nastyz28.com/camaro/zsusp.html and see what ratio you have.

Regards,
MadMike

A 3 series 12 bolt car has a casting # 140, a 4 series has # 174.

Thanks for the help guys. I went out and looked at the cases. The 12 bolt has cast into it the following numbers oposite the end where the ring gear bolts:
ED 30140PM1

From what you said, this should be a three series.

The 10 bolt has cast:
EDB 30117

Any ideas what the 10 bolt is?
Mike all I have is the posi unit. I didn' come with the gears or housing.

With a number like that (EDB30117) - sounds like a 1970'ish 8.2" 10 bolt.

Yeah , EDB 30116 is a 3 series 8.2, so the other has to be real close, probably a 4 series posi., if I were to guess.The # 32118 is a 2 series 8.2 10 bolt.

[This message has been edited by Doug G (edited 12-12-1999).]

[This message has been edited by Doug G (edited 12-12-1999).]