deadeyejedi

can anyone give me any info on this rear end on my 1972 cutlass by looking at the pic ?is this an o type.it is a 12 bolt and to me looks like minimal wear .my brother in law says he can build me a posi using my existindg setup .thanks

csouth

Count the ring bolts. If it is 10 bolt ring and 12 bolt cover its a type O.

joe_padavano

1970 was the last year for the Type O axle, and 1969 was the last year for the Chevy 12 bolt in a Cutlass (for Canadian-built cars). The only factory-installed axle in a 1972 Cutlass would have been a corporate 8.5" ten bolt. The Olds versions used bolted-in axle shafts, not C-clips.

csouth

I know that, but that's assuming someone didn't swap in an Olds type "O" like someone did in my '72..... Would have saved me a lot of money if the 8.5" was there as originally built.

deadeyejedi

ok got it. so regardless of the number of bolts on the differential cover ,the ring would only have ten bolts (assuming the rear is original).and would also be c-clip style.

csouth

If its 12 bolt cover\10 bolt ring and bolt in axles, it is type "0" Olds axle. The Chevy axle will have 12 bolt cover and ring with c-clip axles. If you're lucky, its a Chevy.

joe_padavano

My post was for the benefit of the OP - who apparently didn't really read it.

From above:

csouth

Gotcha

deadeyejedi

yeah i read it just to quickly i get now thanks

monzaz

Caps are a dead give aWAY. !2 bolt cover 10 bolt ring and those caps are all pointing to 12 bolt olds with Bolt in axles. 28 spline axles as all 31 spline axled 12 bolt olds rears were posi. (w30 cars 672 carrier)

Also you will have U bolts to hold the u-joint in where as the 10 bolt 8.5 will have 4 bolts and 2 straps.

Jim
J D

Fun71

Jim,
I have an O-Type that doesn't fit that scenario:
TL code, 3.42 gears, 359 casting number open diff, and 31 spline axle shafts.

monzaz

That would be a first here. Jim

I wiill update my records with the 359 casting being the open 31 spline 4 series carrier.

deadeyejedi

although im 99per cent sure this is the original rear end ill assume nothing . ill take it apart to be sure its 28 spline 10 bolt ring gear i would like to change the gears as well .any recomendations on where to buy the gears and carrier all in one package ?

csouth

If its a type O in a 72, it is not original. Should be 8.5 10 bolt. Monzaz would be able to help you with options for that rear.

oldsmobiledave

You are 99% sure but 100% wrong. Type O was discontinued after 1970.

Jim at JD Race aka Monzaz can sell you everything you need.

deadeyejedi

I never said it was an o type .I asked if it could be identified by the pic .

Fun71

Yep, and monzaz confirmed it was an O-Type so it is not original to your car.

csouth

Just contact Jim(monzaz). He's well versed in retrofitting posi's and newer gear's into these type O housings. I was talking to him years ago about doing mine, but I pulled it for a 9" which better suited my intentions for the car.

jdrace.com