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Discussion Starter · #1 ·
I have a i believe to be from a nova it is a 8.5" 10 bolt rear 28 spline axles going in my 55. I have found a posi unit with gears for sale that came out of a 1976 CUTLASS 442 he said its all factory stuff no good pictures but these can be rebuilt correct? He said the only numbers on it are
ring gear is stamped 5046 41 10 usa 3 y an odd symbol 1 s the side oposite the ring gear is stamped 96 cast in it are the numbers 726, 96 bx
The only numbers I know out of it are 41 10 which should make it 4.10/4.11 gears but could anyone tell from the other numbers if it is for a 8.5" 10 bolt or did they even come in a 1976 442
 

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Through the 60s and early 70s, Old/Pontiac had their own version of a 10 bolt axle, as well as a 12 bolt axle. At some point I think they went to the 8.5" 10 bolt, not sure when or how to id parts. You likely will need a side by side comparison between known and unknown parts. The numbers stamped on the gears don't mean much except for the gear ratio.
 

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My sister has a 77 Cutlass that was bought by our parents new, it has an 8,5 ring & pinion the same as 8.5 in a Chevy except no C-clips and it came from the factory with tapered roller bearings on the axles. It has 2.41 rear gears and I installed a Posi out of a late 70s Camaro for her Birthday about 10 years ago. The factory would never have installed 4.10s in one of these cars. My Hollander book say G bodies from 73-77 could be type O or C.
 

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Those are after market gears, not GM. You need to get the casting number off of the differential. The 2 series is 410409 and the 3 series is 410408. If this is a 410408 then you can use it, but you can't rebuild it. The parts are no longer available for these differentials. The clutches were still available until about a year ago, but now nobody has them.

Notice that the larger numbers are 8s. If this was a 410409 the larger numbers would be 9s. Sometimes it's hard to tell the difference between the 8 and 9 in the smaller numbers. You can see that the 8 in 410408 is not clear in this case.
 

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Discussion Starter · #6 ·
The best I can tell it does have a spacer the guy never has got back with me on any other numbers or anything else I asked about it tho.
 

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Spacer+horsepower=bad

I sheared off all 12 bolts (Camaro here) that hold the ring gear onto the carrier, TWICE, in a rear end set up using a spacer. I bought the car set up this way, after the second time I had it built the right way!

Good luck

Clint
 

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My 67 Camaro SS 350 with a 12 bolt has had a spacer behind a used set of 410 gears for over 30 years no problems, I wore out a lot of slicks untill I put it back on the street with a 4 speed in the early 90s. When I put the 67s SBC in a striped down 75 Camaro with 4.56 geared 70 Camaro 12 bolt that $&!# started happening. The 70 Camaro 12 bolt now has a 4 series Carrier and the 75 Camaro now has a Dana 60. I have a 4 series carrier & another 3 series with 373 gears, for the 67 just in case. In my experience spacers may or may not be a good thing.
 

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Discussion Starter · #12 ·
Thanks for all the advice I let that one pass im still on the lookout for a posi carrier to hold 4.11 gears for my 8.5" 10 bolt if anyone has one or can point me in a good direction for one.
 
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