[attach]Type O rearend detail 006.jpg[/attach][attach][attach]Type O rearend detail 016.jpg[/attach][/attach]

 

Whats the simple posi upgrade here, 455 w/400 turbo trans in gm a body.

 

I can't make out the numbers before "GM" on the edge of the ring gear. Those would be the number of teeth on the ring and pinion gears; divide them and you get the ratio, then once you know the ratio you will know what series carrier you need.

The other info is just the axle housing, which doesn't tell you much about the gears inside it. The gear ratio is what will determine which carrier you need.

 

The carrier has a 358 cast into it. does that help.
the ring numbers look like 14 A 39
The two letter axle stamp is SA
Confirmation on the numbers, I counted the ring and pinion

 

Hard to say from that pic other than an open differential. There has to be another number to the left of that 4A. Is it by chance a 37?

 

39/14 = 2.78


Sounds like a final drive ratio to me.

 

Where did you find the 39 on that ring gear Chris?

 

Yes 39/14. I counted the ring and pinion. We also have an SA code. This sounds like a one legged freeway machine. Is there anything good about this rear end?

 

SA code was for 2.73 in 1971 and 72. Is your car by chance a 1970 Cutlass? That would match the SA code for 2.78.

 

Not a '70 Cutlass, This was in a '67 GS400 I acquired. nothing in the drive train was original and the upgrades seem to be valueless. I'm new at the BOP so I am learning here. Any suggestions on a direction I should take. build this or look for a factory posi. If so, what rear end will bolt up.
Thanks for the help. hours of research here.

 

Evidently I pulled it from thin air.

I thought it was in the picture provided, but now I do not see that in the picture

 

Without seeing the axle it's hard to say. If it's a 12 bolt O style - it's hard to get gears. If it's a 10 bolt 8.5 it's a great rear end to modify to your liking IMO.

LOL so now you're clairvoyant to boot...good guess BTW!!