9 inch vs 12 bolt
02-26-2008, 01:14 AM
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9 inch vs 12 bolt What are the main differences between the two. I have a 9 inch, not yet installed and Im curious?
I once heard that only the 9 inch can really take abusive launches, one after another...maybe just a fallacy.
I once heard that only the 9 inch can really take abusive launches, one after another...maybe just a fallacy.
02-26-2008, 01:20 AM
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A 12 bolt can too. Just not on our cars with the torque arm set-up we have. On a 500whp 70 chevelle a 12 bolt is fine. And of course it also depends on what your stuffing the rear with.
Anyway, for our cars I dont think a 9" cant be beat for the strip. And a midwest set-up, in my opinion, cant be beat right now. Its lighter than a standard 9 and he can build them virtually however you want. And for prob only a tad more than a standard 9"
Anyway, for our cars I dont think a 9" cant be beat for the strip. And a midwest set-up, in my opinion, cant be beat right now. Its lighter than a standard 9 and he can build them virtually however you want. And for prob only a tad more than a standard 9"
02-26-2008, 10:12 PM
#4
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12-bolt has a 8.75" ring gear, the 9" is of course 9". Thats only a 1/4" difference, I've seen plenty of 12-bolts take some serious abuse.
Peace,
Craig.
Peace,
Craig.
02-27-2008, 04:09 AM
#5
Put a 12 bolt into a early Chevelle, Nova, Camaro, etc and you can beat the crap out of it, and not hurt anything. Put one into one of our cars with a torque arm, make a couple 4000 to 5000 dragstrip launches, and I can just about guarantee you'll pick up gear noise. If it is a drag only car, you'll never know or care about the gear noise. Drive your car home from the track, and the noise will drive you nuts. I feel the torque arm stresses the 12 bolt housing, causing distortion. We have never seen this happen with the 9 inch housing.
Exotic Performance Plus strongly recommends the Moser nine inch. This rear is even tougher than the Moser 12 bolt, and the horsepower of the late model F Body cars keeps escalating every year, which requires a very strong rear. With the recent introduction of the 6.2L GM aluminum block and the excellent flowing 6.2 litre heads, the horsepower of these cars is going to just keep climbing at a very fast pace.The nine inch will handle the power, plus we prefer the way the torque arm is bolted to the nine inch in the same way the oem rear-end is attached. (This is the only good thing about the stock 10 bolt...) The Moser 12 bolt uses four short bolts to attach the torque arm, and they have a habit of loosening up, even when loc-tite is used. Why the nine inch is stronger than the 12 bolt. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise.The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, than the 12 bolt does.The 9-inch has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt does. This is not much of a difference, but it is worth noting. Bob
Exotic Performance Plus strongly recommends the Moser nine inch. This rear is even tougher than the Moser 12 bolt, and the horsepower of the late model F Body cars keeps escalating every year, which requires a very strong rear. With the recent introduction of the 6.2L GM aluminum block and the excellent flowing 6.2 litre heads, the horsepower of these cars is going to just keep climbing at a very fast pace.The nine inch will handle the power, plus we prefer the way the torque arm is bolted to the nine inch in the same way the oem rear-end is attached. (This is the only good thing about the stock 10 bolt...) The Moser 12 bolt uses four short bolts to attach the torque arm, and they have a habit of loosening up, even when loc-tite is used. Why the nine inch is stronger than the 12 bolt. The 9-inch has an internal rear-pinion support that also supports the gear end of the pinion to limit gear deflection under high torque loads. This seems to be the major reason why the 9 inch doesn't start whining after high rpm clutch dumps, when the 12 bolt will pick up noise.The 9-inch locates its pinion gear lower on the ring gear to improve tooth contact, than the 12 bolt does.The 9-inch has a 0.125-inch larger ring-gear diameter and internal pinion support than the 12 bolt does. This is not much of a difference, but it is worth noting. Bob
