Strange looking 10 bolt out of a 1972 Monte Carlo

[19,69camaro]

I saw a strange 10 bolt today it was out of a 1972 Monte and it had a finned aluminum cover on the back and on the bottom of the housing where the triangular ears that normal 8.5" corporate usually are there was a half circle about and 1 1/4" in diameter. Now I have heard of some wierd 10 bolts that use a 8.5 inch ring gear with non c-clip axels that can accept all 8.5" posi units but cannot be swapped to another rearend. Can anyone confirm this?

[John Wright]

did it look like the one on the far right?

https://static1.pt-content.com/images/pt/2009/09/rears-1.jpg

[19,69camaro]

No thats not it here I will try to draw a picture. Sorry for the poor paint skills
40959

[19,69camaro]

I think I figured it out the guy mislabeled the add as a 10 bolt and it really is a 12 bolt.

[big gear head]

Might be the O axle. These were used in the Olds Cutlass from '68 to '70 and a few found their way into some Monte Carlos and other A body cars. These have 12 bolts in the cover and 10 in the ring gear.

[19,69camaro]

It ended up being a 12 bolt. The guy was wondering why he wasn't able to sell it. Unfortunately it wasn't a posi like he listed it as. Good thing I cracked it open as I was able to get it for a fair price. I would really like to do a lot of autocross and hit some roadrace tracks. So far the plan is to start with a clean slate because when I opened it up there was a fair amount of rust and the axles were junk. Let me know what you think

Moser replacement c-clip axles 30 spline
Eaton Detroit Truetrac Differential vs Moser (Eaton is $70 less)
Summit Roadrace Ring and Pinion Gear and Installation Kit Pro Packs with Richmond 3.73:1 gears (engine will be efi lsx with f-body t56)
Moser axle bearings
Moser Engineering Aluminum Differential Cover (is this functional at all or is it all show)

Now should I go the c-clip route or go with the the moser housing ends with the larger ford tapered bearings. Which from what I understand eliminates the need for c-clips, but also need to be jig welded on. Right now Im a little overwhelmed. I am on a pretty tight budget (college student) but Im working on my build slowly so if need be I will save up for the better parts because I only want to do this once. Also where is a good place to find all this stuff. Summit seems to be the cheapest and I can combine shipping but if there is another dealer Im all ears.

[big gear head]

First of all, are you sure that this is a Chevy 12 bolt? Count the number of bolts in the ring gear, not just the cover.

If you go as far as to weld on Moser housing ends then you might as well sell the rear end that you have and just buy a Moser 12 bolt. It would be a better rear end in the long run. I'm assuming that you don't want to do that, so just use the c clip axles. There are better parts than the Summit stuff. The Moser cover is a T/A Performance cover with the Moser name on it. These covers are good, mostly for drag racing where the shock load is high. For road racing it's going to hold about 1 more quart of oil and that's about all it's going to do for you.