matt506

I have heard and read a lot about these axels. What exactly makes a O axel one? Is is the fact that they are bolted to the tube ends instead of being held in by a c clip like a Chevy? Matt

Fun71

The O-Type is a rearend made by (for?) Oldsmobile from 1967 to 1970. They have an 8.5" ring gear and a 12 bolt diff cover.

oddball

In the crazy days of 65-70 when the GM lines were consolidating common parts, there were lots of oddities. The O axle is one of them. Olds designed it before the now-common c-clip 10 bolt. But, since the consolidation was happening, there are still a lot of similarities.
The external critical dimensions (mount points, tube ends, flange ends, pinion location) are all the same across a bunch of the rears. The O can be thought of a hybrid between the 12 bolt and the 10 bolt with bolt-in axles. It uses unique (or at least very seldomly used otherwise) bearings, has strength somewhere between the 12 bolt and 10 bolt, and uses bolt-in axles. The O rear shares very few parts with any other rear end.

Olds switched to the bolt-in 10 bolt which shares a lot of parts with the c-clip except the axles are bolt-in, so the axles and axle bearings are different. It's a better rear than the c-clip but the manufacturing costs aren't as high as the O rear since most of the parts are common.

joe_padavano

The "c-clip" ten bolt axle was first used under the 1964 Chevelles. The Type O was first released in May 1966.

http://wildaboutcarsonline.com/membe..._Diff_1-12.pdf