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I was told that a 1970 ss 10 bolt was stronger than a 1970 ss 12 bolt. I say that the 12 bolt rear was stronger. They were both available in 70. Anyone want to offer an opinion?
10 bolt vs. 12 bolt
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70 SS didn't come with a 10 bolt... :noway:
12 bolt is a bit stronger, yes. :yes:
12 bolt is a bit stronger, yes. :yes:
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The SS didn't have a 10 bolt because it wasn't strong enough for big block power. The 12 bolt is a good bit stronger than the 10 bolt. In '71 GM started using the 8.5 10 bolt, which was stronger than the old 8.2 10 bolt, but still not as strong as the 12 bolt.
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You were told a myth, for the reasons note above. They probably meant well.
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Or they were trying to sell a 70 10 bolt.
Spot on!
Not a BBC thing, 12 bolts came behind just about all cars with 350 4 barrel engines or larger.
It was a Heavy Duty thing...
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You guys all told me what I thought to be true, but a suposedly very knowlegeable chevy guy told me about the 10 bolt theory whaich I had never heard of before. Just checking out the stories.
Thanks,
Roland
Thanks,
Roland
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Yea, I just tossed the big block thing in because he said '70 SS and the '70 SS had a big block. I had a '67 Malibu 327 4 speed that came with a 12 bolt.
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Bigger axle shafts, bigger pinon, stronger housing, bigger ring gear.
c clip axle retention is actually a very good way to retain the axles, and they seal much better. Problem comes when an axle shaft breaks, then the c clip is bad. Only reason to convert is for drag racing, or off roading.
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As far as I know all rear ends are rated by the ring gear diameter. The larger the ring gear the stronger the rear end. That doesn't take into account the axles or other parts. A 7.5 rear end with 35 spline axles is a total waste because a 7.5 rear end isn't strong enough to break a 28 spline axle. There is nothing that you can do to make it stronger because the gear is just small and weak. A 9 inch Ford is quite a bit stronger because of the much larger ring gear, but many of them came with 28 spline axles. You can upgrade the axles to 40 spline and the whole rear end is stronger. You are not limited by a tiny ring gear. Leverage is what makes a larger ring gear stronger. Even a 1/8 inch increase in the ring gear diameter can make a difference. GM upgrades the 7.5 rear end by 1/8 inch in '86 to make it stronger and they upgraded the 8.5 rear end by 1/8 inch in '98 to make it stronger.
I witnessed a friends axle come out at 35 mph and destroy the quarter panel on his 70 elcamino..,.radial street tires. I'm sure the thing got beat on quite a bit but not with slicks....he pulled from the parking lot at work and was just driving normal and out it came. Probably just a fluke but it sure did a lot of $$$ damage.
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i thought the 9" was stronger because all the bearings are beefier, it has that third support bearing on the end of the pinion gear, and the angle that the pinion and ring gears mesh at provides a larger contact area but uses more energy to turn?
i've always thought that an 8.2 is weaker than a 12 bolt because everything is smaller and lighter, and not necessarily because of the diameter of the ring gear which is just one of many things that aren't as beefy, and that an 8.5 is almost as strong as a 12 bolt because they made everything almost as beefy as a 12 bolt.
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Any time the ring gear diameter increases the potential strength of the rear end increases. It's leverage and nothing else. That's why top fuel has been increasing the ring gear diameter in their rear ends for many years now. I remember when they were using 9 inch Ford gears, but now they are somewhere around 11 inches. There are several things that make some rear ends better than others, but the ring gear diameter is always the number one reason. If you took 2 rear ends with a 9 inch ring gear and one of them was the 9 inch Ford and another one only had 2 pinion bearings then the Ford would probably have a slight advantage over the other one. The 8.5 10 bolt is stronger than the 8.2 because the ring gear diameter is larger. The 8.5 is not as strong as the 12 bolt mainly due to the ring gear diameter, but the differential bearings are also smaller. The pinion shaft is the same at 30 splines, but the 9 inch Ford only has a 28 spline pinion, so I don't think that has much to do with it.
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With regard to ring gear size, and ignoring things like axle spline counts, housing strength issues, bearing limits etc., in this case it really is a matter of size.
In a hypoid spiral bevel gear, there are actually several teeth in some degree of contact at the same time, sharing the power transmission between them. A hypoid type spiral bevel gear (typical classic car differential) can transmit more or less power based on the size of the tooth contact area and the surface area of teeth simultaneously engaged. A larger diameter gear allows for several advantages.
Speaking strictly of gear design issues, A flatter contact area allowed by a larger ring diameter results in a larger contact area, allowing for distribution of force over a larger area, with obvious attendant durability, power transmission (and lubricant life) advantages.
Besides the things mentioned by the other guys, larger gear diameter allows room for additional ring gear fasteners (bolts and bosses) which effectively reduces the load on each fastener. Larger ring means larger carrier, which can allow for more robust spider gears, etc.
Finally, don't kid yourself about "only .375 bigger" either. In the world of high strength gear grade alloys, that's a lot of additional material.
GM was building to a cost point, with very specifically calculated torques and vehicle weights. They were NOT consciously building racing equipment.
In a hypoid spiral bevel gear, there are actually several teeth in some degree of contact at the same time, sharing the power transmission between them. A hypoid type spiral bevel gear (typical classic car differential) can transmit more or less power based on the size of the tooth contact area and the surface area of teeth simultaneously engaged. A larger diameter gear allows for several advantages.
Speaking strictly of gear design issues, A flatter contact area allowed by a larger ring diameter results in a larger contact area, allowing for distribution of force over a larger area, with obvious attendant durability, power transmission (and lubricant life) advantages.
Besides the things mentioned by the other guys, larger gear diameter allows room for additional ring gear fasteners (bolts and bosses) which effectively reduces the load on each fastener. Larger ring means larger carrier, which can allow for more robust spider gears, etc.
Finally, don't kid yourself about "only .375 bigger" either. In the world of high strength gear grade alloys, that's a lot of additional material.
GM was building to a cost point, with very specifically calculated torques and vehicle weights. They were NOT consciously building racing equipment.
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That's no good. But, they're good until the axle shaft breaks!
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