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

 

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

 

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.

 

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.

 

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.

 

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.

 

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

From above:

 

Gotcha

 

yeah i read it just to quickly i get now thanks

 

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

 

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.

 

That would be a first here. Jim

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

 

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 ?

 

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.

 

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.

 

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

 

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

 

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