Completely new to rear end work but have lift and time. Can I upgrade the stock r/e to posi or do I have to relpace the entire r/e axle set up. I plan on rebuild the current engine/tranny around 400hp. Thx

 

You should be able to buy a posi carrier assembly and install in your current differential with whatever ratio gears you want to run.

 

Which rear end do you have?

 

If your car is /was a 455 car it will be 12 bolt cover with 12 bolt ring and it is a FULL SIZE OLDS 12 bolt 9.3 rear (parts are NOT AVAILABLE from the aftermarket BUT I do have a complete 2.93 posi here for sale)

If your cover is 10 bolts and looks like a 1/2 ton chevy or GMC truck rear center section you have a 10 bolt 8.5 and you can buy MANY parts for this rear differential

Last you might have a 10 bolt cover 12 bolt gut PONTIAC full size car rear it was for intermediate (v8 but not high horse) powered Full size cars... There are 3.55 gears for sale in the aftermarket and the posi units are a bit easier to find than the 12 bolt olds units and gears. Have these posi units and gears too.

Pictures are below-

 

I have the 12 bolt patten and it is 455 full size

 

Call Jim on the 2.93 posi. It's probably the best gear you'll find for that rear without a very long search.

 

yES THESE ARE HAD TO FIND for sure. I have only seen 3.08 and heard 3.23 better. They might have a 3.42 BUT I have not seen or heard one found yet in the 12 bolt FULL SIZE olds rear.

BUICK 65-70 YES...