I know i asked this a while ago but after getting in to an arguement with my dad i figured i better get my facts straight. A friend of my dads has what he said a 12 bolt out of a 72 olds cutlass (and he knows a lot about cars, but i didnt know that there were 12 bolts out there that had 12 bolts in the cover and only 10 in the ring gear). Now knowing that, everyone said that there are 12 bolts in the cover and 10 in the ring gear of this rear end, but is that true for all of the olds 12 bolts or could one out of like a 442 maybe be a true 12 bolt? Just trying to find a a sturdy rear end for '71 Chevelle, and its not too easy. Thanks guys

Some of the non Chevy GM cars got the Chevy 12 bolt rear end, but most didn't. The "O" axle has a 8.5 ring gear with 10 bolts and 12 bolts in the cover. The Chevy 12 bolt has 12 bolts in the ring gear and the cover.

Thanks BGH Im hoping that this rear end has 12 bolts in the ring gear.

The Olds 12 bolt, like was said, has a 10-bolt, 8.5" ring gear. It's a fairly strong piece, and it has bolt-in axles, which is nice... BUT, I don't believe rebuild kits for them are too prevalent, and gears - if you can find them - will probably be fairly pricey, with a small selection of gear ratios.

There are several popular gear ratios, along with new 2 and 3 series limited slip (posi) differentials stil available for the "O" axle. They are more expensive than the Chevy parts, but still affordable.

What would be the better thing to buy? I could pick the "O" axle cheap but if the parts are more, what about good axles (like 32 spline if that is a good idea, in a moser, or something of the like?)and a posi unit and gears and bearings etc... how much would that be? Or should i just look for a 12 bolt (chevy one)? Thanks for all your help guys.

You can get Moser axles for it, but you can not increase the number of splines. As far as I know the only differential available is the Traction Lock, which is what came in them from the factory. There might be an Auburn for it, but I think the T/L would be better. I haven't sold one in a while, but I think the T/L is around $500. The Moser axles would be about $375. I can get you a price list if you are interested. The 12 bolt Eaton posi is $360 and a set of 12 bolt c clip axles is $235 for comparison.

well thanks that anwsers my question to as i am in the same boat with this rearend i am looking for a chevy 12 bolt ed

Thanks BGH I might just look for a 12 bolt chevy but how hard are c-clip eliminators to put in (could i do it my self) and are they ok for street mostly (but there will be a few strip passes)?
I feel stuck between a rock and a hard place b/c there seems to be advantages to the "O" and the chevy but i have the "O" at my disposal, i just hate to put a lot of money into it as apposed to less money in a 12 bolt chevy. Also can you get aftermarket stronger covers for the "O"? thanks for all your help guys

The c clip eliminators are not too hard to install, if you are good with a hack saw. This ruins the housing if you ever wanted to go back to the original axle bearings. The c clip eliminators have a BAD reputation for leaking gear oil all over your brakes. They are not recommended for street use, but some people successfully run them on the street. They cost about $155, so add that to the total for building the 12 bolt and see how it compares to the "O" axle.

BGH if you could get me a price list that would be great, and much appreciated too. I might go with the "O" axle but im not quite sure. You said i cant go with any more splines on the axles? i think it has what 28 spline? do you think that would hold up to so abuse (mostly street with some strip and hard driving)? If you would get a prices on a gear set, axles (moser preferably) a posi unit, rebuilt kit (bearing etc...)and if i can get a strengthened cover that would be great, im still on the fence if i wanna get this rear end or go with a 12 bolt. thanks for your help.

if anyone is interested i have two 1967 olds 12 bolt cover/ 10 bolt gear rears. email direct to me. tom

I'll get some prices together for you.

BGH,

What about sawing off the Olds rearend's axle ends and welding them back on a Chevy 12-bolt housing to get bolt-in axles??

Then get custom 12-bolt axles that would take the Olds wheel bearings and lock rings..

pdq67

You know, like converting a 12-bolt to the 9" axle retention system.. Use a jig of course sorta deal.....

Here are your prices. Are you sitting down? The differential is $533, the gears are $329 and the axles are $309. This does not include any bearings or shipping. There is no heavy duty cover for this rear end. You will probably be looking for a 12 bolt Chevelle rear end.

Thanks BGH thats what i was thinking, b/c even though the olds has bolt in axles, im not running so much power that i would need to switch a 12 bolt chevy to c-clip eliminators. Plus i would like some higher spline axles so i will just go with the chevy. Thanks for all your help.