Screecher

I been reading just about everything I can find about GM type "O" rear ends. So I finally decided to join the forum to get the answers. I have a 1970 Olds Cutlass Supreme Convertible with the following rear end housing and gear.

Housing: 402227
Carriage: Series 2
Ring Gear: 2.56 (Non-Posi), I know it's crappy....

I want to know if a series 3 carriage will work with a new ring & pinion gear in a #402227 housing? (I'm looking to go posi with a 3.08 gear ratio) Would the existing axles work with a series 3? Are the bearing the same size? And finally, I'm about 95% sure that the ring gear in it is a 10 bolt 8.5" but I keep seeing various posts that say it's a 8.2". Which is it?

brddg

Supercars unlimited has a great info page on diff ID and carrier/gear info. You can check that out or get a hold of 507olds (Brian Trick) he's got great info and may have parts you need. Welcome to CO!

Screecher

Thanks for the info, I've already looked through what supercars has online but I was looking for a little more technical and a lot more on compatibility with my particular housing. I appreciate the help.

2blu442

The type O has a 8.5 inch ring gear, 10 bolts holding the ring on the carrier. If you can find a Type O 3 series carrier it will fit in that housing. The 3.08 would use the same 28 spline axles that you have now. Someone else will have to speak on the bearings.

John

Screecher

That's great news! So as long as I stick with a 28 spline carrier the axles will work. I just wanted to make sure that the length wasn't different on the series 3. Thank a ton for the info!

Fun71

The bearings are the same for the various 28 spline carriers.

507OLDS

The gears are going to be the hardest part to get.Nobody is making anyuthing aftermarket for them at the moment,but the posis are available.A lot of the 67 O-axles came with 3:08's,so you might be able to find a set of 3:08's that way.The new posi units will fit those gears.
The 12-bolt O-axle has a 12-bolt cover,10-bolt ring gear,and 27-spline pinion stem.
The axles are 28-spline,with the exception of the optional 31-spline axles that were offered late-67/68. All of the axle shafts are the same length,67-70.

Screecher

OK Gentlemen, to add to the insult of my "O" differential issues, as far as I can tell the posi rear ends and limited slip are the same whether it is a series 2 or 3 carriage. The only difference I see is an additional stabilizer between the lower control arms on the posi factory rear ends. If I go posi, so I need to stabilize the rear end to prevent torqueing?

oldsmobiledave

Stop calling it a carriage. Horses pull carriages. You mean a CARRIER.


The boxed lower control arms have nothing to do with the gear ratio or the carrier nature (open vs anti-spin). The boxing is part of the FE2 suspension & includes the boxed lower control arms & the rear sway bar.


There are 3 carriers. One for 2.56 & 2.78 gears. One for 3.08 & 3.23 gears & a 3rd for 3.42 & numerically higher gear ratios (3.91, 4.33, 4.66 & 5.00). The aftermarket Richmond gears (not currently available except used or NOS) can be used only in the OEM 3.08 - 3.23 carrier.

Fun71

Yes, that is correct: posi and limited slip are the same thing. This was covered before in another post.

Yes, the rear housings are the same whether they have a posi/limited slip carrier, an open carrier, 2.56 gears, or 3.91 gears.


There are two main differences to know about regarding O-Type 12 bolts:

1) The early ('67-'69) rear housings use different axle shafts and axle bearings than the later '70 version, so axles and bearings are not interchangeable.
2) There is a HD version of the early O-Type that has 31 spline axle shafts, so some of its parts are not interchangeable with other early O-Types.