yamahondarider

So I've been reading a bit about the O type rears and the info is a bit mixed but from what I understand you can't get a damn aftermarket part for em. Whats the deal here, can I buy a set of 3.73 GM (Chevelle) 10 bolt gears (ring and pinion gears) off ebay and bolt the ring onto my O type carrier? Will the pinion fit in the O type housing? Yoke? Will the usual $50 GM ebay mini spool fit or are the Olds axles/carrier unique in some way that it wouldn't? The specific rear diff in question is the 12 bolt cover, 10 bolt ring gear O type diff in my '69 Cutlass S auto, 2 bbl, non-posi open diff car which I believe has 2.73s but I haven't pulled it apart to check. I'd hate to have to spend a bunch extra for O type specific gears and mini spool. Any info is much appreciated. Thanks guys!

TripDeuces

My advice.................don't put a spool on the street.
There are several members on here who work on rear ends. I'm sure they will chime in soon and will have everything you need for your project.

joe_padavano

One more time: NOTHING from other GM axles interchanges with the Type O. If it were possible to use the 8.5" ten bolt gears, we wouldn't be having this discussion. It is a completely unique axle used only in Cutlass cars from the late 1966 model year through the 1970 model year.

oldsmobiledave

2.73 was not a gear choice for the type O. 2.78 gears were.


The easiest way for you to end your frustration is to sell off your Type O 12 bolt & buy any other differential for your car. That way you won't have to deal with the reality of the Type O 12 bolt & its' limitations.

70cutty

Best thing you can do is look for a rear out of 71-72 cutlass. Readily available parts, bolts right in and it has bolt in axles.
I did have to shorten the driveshaft a bit. $80 to cut and balance.

I found mine on CL for $200.

70cutty

Here is one right here on CO for $150.

https://classicoldsmobile.com/forums...-rearends.html

yamahondarider

Thanks guys. Looks like I'm gonna be ditching the O type. Too much of a hassle to get gears for. 70cutty, thats not a bad price, too bad its such a far trip. I'm in upstate NY. Cheapest A body rear I found within 200 miles of me is a 3.08 posi out of a GTO for $500, hopefully I can come across a cheap open diff to throw gears and a spool in. Its nuts how many people want upwards of $1000-$2000 for a stock non rebuilt posi 3.73 or similar.

gevosrears

I`m in upstate N.Y. also . You can call me at 315-568-9744 .
John , Gevo`s Rears & Gears www.rearsgears.com

monzaz

There is NOTHING wrong with the 'O' rear.
3.42 and 3.90 gears are available Posi units eaton - trac lock power trax and rebuild kits are all available.

Axles are BOLT in that is a GOOD thing and in the day 12 bolt 'O' rear was IT
67 68 was a bolt in 31 spline rear that rivaled the c-clip 12 bolt chevy rear.

The rear is also correct for your Olds

You have the rear and all you need are parts. Your just not talking to the right people.

Good luck on your decision... We have all the rear from 10 bolt 8.2 Olds 12 bolt to 8.5 and beyond. Jim

JD

Fun71

Gear sets are not as readily available as those for the 8.5" 10 bolt, and therefore they are more expensive.

I remember reading that mini spools and "lunchbox lockers" such as Lock-Rite, Spartan, etc for the 8.5" 10 bolt will work in the O-Type.

yamahondarider

I definitely see the advantage to bolt in rear axles, I was actually really glad to have that rear when I first heard about it. Then I looked at the prices for parts and I died a little bit inside. Chevelle guys have it so good with their cheap parts and availability . I just can't bring myself to spend more than I have in the ENTIRE CAR to get my hands on a rebuilt posi rear with the gearing I'm looking for, or to convert my rear to a posi unit with different gears. Hell I'd just leave the rear alone if it didn't have such bad gear ratios for a manual transmission. I think I'm gonna nab up a $150-$250 Chevelle rear with reasonable gearing and a $50 mini spool so I don't go flat broke. I found a few local after a bit of digging. Just makes more sense money wise. I'll hang on to the rear thats in the car, it is original to the car. Maybe one day I'll come across a good deal on gears and it'll go back in. Or I'll win the lottery.

Good to know, I'll keep that in mind. I'll be buying a spool regardless, maybe I'll toss it in the olds rear just to confirm that for future reference before I toss it in the Chevy rear.

Side note, I also found that G body guys like to swap A body rears into their cars and only need adjustable upper control arms to compensate for pinion angle. I know I know, the 7.5s are weaker. But, a G body rear with 3.73s is like $150 and being a tad narrower I might even get better fitment with my 10x15 wheels. Of course the cost of adjustable UCA's and a conversion U-joint will be factored in. Might be cheaper to try and find a Chevelle rear with steep gears. We'll see what happens.