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Old Apr 26th, 16, 08:22 PM   #1 (permalink)
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12 bolt vs 10 bolt

I have just gotten and 75 Camaro and I'm working on a lot of little projects but one that is comeing up is rear end I started looking for a 12 bolt (8-1/2) and alittle harder to find than I thought but what I wanted to know is a 10 bolt 8-1/2 just as good. what are pro and con

thanks again Cenobitya
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Old Apr 26th, 16, 09:09 PM   #2 (permalink)
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Re: 12 bolt vs 10 bolt

I believe the 12-bolt was only available in 1970. After that GM went to the 8.5" 10-bolt which is not quite as strong as the 12-bolt from what I have read but unless you are putting out serious HP you should be fine. Many people (including me) have put 8.5" 10-bolts in their first gens because they are easier to find and cheaper.
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Old Apr 27th, 16, 02:48 AM   #3 (permalink)
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Re: 12 bolt vs 10 bolt

It has been said that with a few good parts a 8.5" 10-bolt can be as strong as a 12-bolt.

I have said I don't care what axle you use, even a 2.5T Mil. axle, will break if abused too much.

Build what you have and you'll be fine
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1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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Old Apr 27th, 16, 05:06 AM   #4 (permalink)
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Re: 12 bolt vs 10 bolt

The 12 bolt had an 8-7/8th inch diameter ring gear. The AAW "corporate" ten bolt was introduced in 1972 which made 1971 the last year that the Spicer made 12 bolt and the 8.2" 10 bolt were offered (they had been introduced in 1965).

The 8.5 inch ring and pinion isn't as strong as the 8-7/8th inch ring gear as bigger is better. That isn't totally true as the 8.5 inch AAW made rear end uses the same size pinion as is used in the 12 bolt Spicer (same bearing size). But when it was first put under a Camaro it used the ten bolt 28 spline axles out of the earlier 8.2" ten bolt. Power levels where dropping like a stone and the muscle car era was over in 1972 with all engines being made ready to burn unleaded fuel (which didn't hit the market until 1978). Things went from bad to worse as the big block went away in all cars except the Corvette in 1973 (1974 had the last BBC powered 'vette), and engine power continued to fall. In 1994 GM authorized the use of the 12 bolt 30 spline axle in the AAW 8.5 inch rear end. So you can rebuild an 8.5 using everything except the larger ring gear out of the earlier 12 bolt. But you have to put it together, there was no bolt in Camaro rear end made that way from the factory.

Personally I use a 35 spline axle Dana 60 with Ford Torino bearings to get rid of the C-clips. that I buy from Moser to give me peace of mind. The added bonus is the inspection cover has ten bolts so it is still a ten bolt rear sort of as far as originality goes.

Big Dave
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Old Apr 27th, 16, 07:03 PM   #5 (permalink)
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Re: 12 bolt vs 10 bolt

thanks guys this helps me a lot

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