So is it true that I have a 12 bolt rear end with 10 bolt gears in it?? If so how do I find out which gears I have without taking it to a shop, and if I wanted to order some gears for it such as 3:73 gears which ones do I order. All I know right now is that my rear end is non posi (one wheel wonder). I have a TH350 that I am getting rebuilt real soon. I was told that getting a shift kit, stall and gears would make a world of difference. What is a good setup for a stock 350 rocket #395558 2, quadrajet 4bbl, edelbrock performer intake? Just looking to have a little more fun from red light to red light!!!

 

The posi for the olds 12 bolt is made from a ford 8.8 set up you can get them I would look up monzaz (Jim ) or 507olds ? Brain trick

Gears are not currently made for these from my understanding but you can get used/ old stock

Best way to get gearing is to pull cover and there are some numbers to read there are others ways I will let some one else explain the methods

 

There are zero aftermarket gears available for the 12-bolt O-axle right now,and the original GM gears are scarce. There was never a 3:73 ratio for this rear.Your choices,in that range,are 3:42 and 3:90,if you can find them.
A few alternatives are the 71-72 8.5" 10-bolt,or the 12-bolt Chevy. Both of these have plenty if parts available.

 

I know he's a smart guy, but......

 

Lol Brian