Differential change

[Ridgeline]

This is a newbie question. Is it possible to take a non posi rear end on a g body and replace the gears, etc and make it a posi rear end?

 

[85 Cutlass Brougham]

Yes. You just need the right differential.

 

[Ridgeline]

Can you tell me what I would need? The ratio is not a problem, however I would like to be at or below 3.73. Have intentions of having a small block 383 between 350 and 400 horse.
Thanks

 

[85 Cutlass Brougham]

Well, what are you going to want to do? Swap both the gears and diff, or just one or the other? If both, you need gears, a rear axle rebuild kit, a limited slip diff with a 3 series carrier, and the tools to set up the ring and pinion right. Or, you can pay a axle shop to set it up for you for $200 or less.

 

[Vern]

What transmission do you plan to run?

 

[Ridgeline]

It has a 4 speed overdrive in it now. I hadn't really thought that I would change it. I am new to this and this transmission might not be the one I need. I am going to change the whole drive line if needed. I am just trying to get some ideas on what works best and where I can get the parts I need.
Thanks.

 

[Vern]

Two thoughts for ya.. one generally its easier cheaper and you have less chance of screwing up if you can find a used rear. You can sometimes find them drum to drum that already have the posi and acceptable gears in it. You just swap the whole rear instead of tearing into the pig and hopeing you can the right shims and pinion depth. Two if you have a 200-4r overdrive keep it. Just add a GOOD shift kit like the one www.ckperformance.com sells. It does not have to be set up to shift harsh. The cheap shift kits are junk. Last you never said what engine is in the car now.

 

[Ridgeline]

It has a 305. From what I have been reading it's not worth fooling with the 305, just move on up to a 350 or a stroker motor. I am glad to hear about the transmission. I like the idea of the lower rpm at hi way speeds.
Thanks