davidstereo

I have the peg leg 12 bolt "o" rear in my 68. I want to know the best, most cost effective way to change it over to a posi 3.42. Is there an axle I can find in a junk yard to swap over? I would rather find a posi rear with the wrong gears and get new gears for it? Posi units are not cheap. Any help would be great. Thanks

Olds462

I'm am also looking to do the same thing with a 1970 "o" type twelve bolt. Any help from anyone would be greatly appreciated.

Nasty455

As far as I know,all the a bodies from 68-72 should fit.
3.08 posi seems like the most popular that I've been able to locate.

Rickman48

There's 3 or 4 guys that build rears, to your specs for $1200 - 1500.
In my experience, if you don't know how to set the gears, buy a drum to drum unit, as it's a couple - 3 hours labor!

sworthy555

I have a 3.42 posi carrier and the ring and pinion for a 12 bolt O axle that I bought from supercarsunlimited and had it in my SX for about 50 miles and replaced it with a 2.56 posi carrier that I bought from JD Race.

If interested please send me a PM.

DENT

You could swap out the entire axle and install a 12 bolt Chevy .

droptopron

You need to eff around with the driveshaft length then.

507OLDS

Yes,you "could" buy a posi rear,with the wrong gears,maybe get a deal,but by the time you get the new gears installed,and the smoke clears,you will have the same into it.Not to mention,the posi unit itself is over 40 years old,and probably needs some attention.No matter how you cut it,you will end up spending the same amount on the rear.

davidstereo

Thanks for all of your help. If I cant get sworthy's unit then I will just buy new. I think that is the smartest route to take here. I don't like doing things more than once if I can avoid it. dave

davidstereo

i was wondering what year cars have the 12 bolt chevy rear in them? It isn't too expensive to have the driveshaft shortened. gears and posi units are pretty expensive. If I can find a used one with lower miles that might work?

507OLDS

A 12-bolt Chevy is usually more expensive to buy,compared to a 12-bolt Olds.The housings are getting hard to find,thus pricey,when you find one.There are plenty of parts available for them though.