10/12 bolt rear end identification help

[tony_ru]

hi there, got real strange gm axle, it has 10 bolt cover but 12 bolt carrier.
it looks like 12 Bolt 8.75 Corporate from this site
http://www.jdrace.com/diff_id/12b875Corp.htm

but inside i found 30 spline moser camaro axels and 8.875 eaton posi
https://www.summitracing.com/int/parts/msr-a123003/overview/
https://www.summitracing.com/int/parts/etn-19554-010/applications/

so that means parts are interchangeable with normal 12 bolt or not?

i'm planing to swap it in my regal but this axle has no brackets at all and before i start any fabrication i want to be sure i can find parts for that rear end

thanks

 

[DRIVEN]

What you have is a bit of an oddball but it looks like you have it correctly identified as an Eaton 8.75" from the mid '70s. That Eaton carrier number comes back as 64-72 GM 12 bolt 8.875" just like you said. I don't know if parts interchange or not. What numbers are on the ring gear?

Is this rearend going to be narrow enough for your Regal? Seems like all the applications listed in the first link were pretty wide.

 

[tony_ru]

So carriers are the same right? Isn't the carrier for 8.75 rear should be smaller since ring gear smaller too?
It around 61" flange to flange and should be ok with my gta wheels but I need check it of course.
Ring gear have only 41-12 GM and no other number, I found this ratio was extremely rare and there are no aftermarket gears at all

 

[DRIVEN]

3.42 isn't a rare ratio but I'm not sure it's common for your particular application. I can't say the carriers are the same but someone obviously put an 8.875 in your 8.75 housing. But, 7.625 parts go in a 7.5 housing so it's conceivable that the 2 interchange. If you're willing to do some disassembly you could get some bearing numbers and take some ring and pinion measurements to see if you have "12 bolt" parts or something really unusual.

FWIW, there were BOP 12 bolts that had 10 bolt internals. Some of the earlier 10 bolts got bolt-in axles too. Plus, you probably already know, car and truck 12 bolts are different. GM wasn't afraid to throw curve ball when it came to rearends.

 

[TURNA]

No upper control arm mounts.

And its an oddball. I believe that is an Oldsmobile only rear

i would pass on it and save up for a rear that fits and you know what it is.

parts for them are scarce

 

[olds307 and 403]

There isn't a ton of room in the G body wheel well. You will need a very offset wheels to have any hope of fitting it. It should be plenty strong, the factory 8.875" axles were the weak point and it looks like 8.875" car gears would probably fit.

 

[tony_ru]

I would pass on it and save up for 9" too, but since I live overseas shipping will be almost same price as rear end from moser, just don't want spend car price on rear end lol. I can weld all mounts my self, the real question is it too wide for g body? I have gta wheels with 5.25 backspacing, ls1 rear brakes and 235 wide tyres. A lot of work this time so I still not fit it on car, do somebody have any info of how wide our cars fender to fender?
ps sorry for my english)

 

[olds307 and 403]

That rear is 3" wider flange to flange than the G body rear, from the info I found. It has a good gear ratio, a better posi and stronger 30 spline axles. Your tire width is narrow, which will help. Even factory rims might be close, my slicks 8.5" wide slicks rub the frame on 0 offset 15" factory A body rims on my G body. Best to put the rims on the rear an place it behind the car, that will give you a idea on how close it will be.