10 bolt rear carrier identification

[Deni2nd]

Can anyone look at the photos and tell me the ring gear size and the carrier series

[cny first gen 71]

 

That will give you the size anyhow.

[Deni2nd]

It is a BOP rear with 28 spline axles

1 1/4 pinion nut

Left hand thread ring gear bolts

Edge of tooth to edge of tooth ring gear measure 8.5

Can't find info anywhere that there was a 8.5 BOP rear

[Deni2nd]

Do the casting numbers on carrier indicate anything

[Sam (Bones)]

the gear gear is stamped 41 & 15 so that's a 2.73 gear so a 2 series carrier

[72MC]

That looks to be a Pontiac 10 bolt rear in 2:73 posi.  The "half moon" shape at the 3 and 9 o'clock position on the case is the key.  It is part of the BOP line of 10 bolt rears but is considered the best of that line of rear ends.  Does the cover have half moon shapes at 3 and 9 o'clock?  - dave

[Deni2nd]

Yes it does have the half moons on the rear cover.

As I have been reading all I see is the 8.2 ring gear. But mine has all the identification of a 8.5 ring gear size. Do you know if they came with a 8.5 ring gear?

[tonym0828]

10 bolt 8.5 inch GM corporate rear end

 

If it is A 12 bolt BOP they had 8.5 but gears not interchangeable with chevy 10 or 12 bolt

 

I have a 72 Monte with7.5/7.625 rear end. axle code says it is 2:73 open. Now it has a weird rear cover that looks like a 10 bolt 8.5. After some searching I found GM used these in some 70 - 72s like cutlass, GTO and Monte Carlos. It says they have the bolt in axles but did not say if they were BOP.

[72MC]

Donald, the pics above are missing your type of rear end.  The Pontiac 10 bolt cover has scallop shapes at the 3 and 9 oclock position.  The Pontiac 10 bolt was a 8.2 rear but was considered stronger / better that the BOP 10 bolt and the GM 10 bolt in 8.5.  Will it handle the power a 12 bolt can handle?  NO.  But they were sought after rear ends for guys with engines such as 327 s etc. Check out this site:

 

http://www.oldsmobility.com/old/10bolt-tech.htm

 

- Dave

[72MC]

[Deni2nd]

Please see photos

This rear has a pinion nut size 1.25

It also has left hand thread ring gear bolts

Although I don't have a picture of the rear cover it does have the scallops at the 3amd 9 position

[72MC]

Bottom line is this.  You have a Pontiac 10 bolt posi in 2.73 gear.  Carrier is obviously a 2 series.  If you don't like the rear, I think there is at least a "cult following" market for them that you could get some money for a bigger stronger rear.  That rear will only serve you properly with a stock to mildly built street small block in front of her.  - Dave

[Deni2nd]

Dave

Thanks

It's not that I don't like the rear. I do prefer bolt in axle want to change the rear gears even if that means changing the carrier.

I just can't be sure what to order. Everything I read says a 8.2 carrier and ring gear but there's the rack it has a 1 1/4 inch pinion nut it also has left hand threads on the ring gear. And the housing has the lugs on the bottom at the 5 and 7 o'clock position

My rear is the bolt in axles.

 

The1971-'72 Buick GS/Skylark and Olds Cutlass A-body 8.5 10 bolt did not have C-clip axles.

The non C-clip 8.5" 10 bolt, type "C" rearend was used in some 1969-'72 Pontiac GP and 1970-'72 Monte Carlo.

There have been non C-clip rearends found in Chevelle wagons, and some El Caminos through at least 1974.

[72MC]

If you want to keep and rebuild that rear, make sure you deal with someone that knows that there is a differance between a BOP rear, GM rear, and a Pontiac 10 bolt.  I always had great success with my builds using Randy's Ring and Pinion.  Their website used to be user friendly.  Hopefully it still is.  I believe they are out of Washington state.  I had a Pontiac 10 bolt at one point but disposed of it so I could concentrate on 12 bolt rears only.  Enjoy the build. - Dave