12 bolt limitations?
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.
How much power can it hold? It is hard to say, the 12 bolt gets noisy but I've seen them handle 500 to 600 rwhp quite often. 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.
How much power can it hold? It is hard to say, the 12 bolt gets noisy but I've seen them handle 500 to 600 rwhp quite often. Bob
Teching In
Joined: Sep 2008
Posts: 26
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From: ELGIN
what about a strang 12 bolt with 33 spline axles?? and full spool 700 to 800hp im building hopefully a badass nitrous setup 403ci big shot and i have a strang 12 bolt hopping it will Handel the power?? what you think
8 Second Club
Joined: May 2004
Posts: 371
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From: Savannah, TN
The nine inch is a stronger rear and one more perk is unlimited on gear ratios. But I run a 12 bolt in my car has been pulling 1.30 to 1.35 60s for 3 or 4 years . I have hurt one gear set and that was after i broke a 33 spline and had to change spools because the gave me a new set but they had to be 35s. it was the first hit out so i think when we broke the 33 it hurt the gear. I put a new set in and have went 5.20s and 8.18@ 177 with this rear. and the loudest rear i have ever heard was a 9 inch in a f body with 3.90 gears and it was new the guy even sent it back to have it checked and they said it was good. 4 years latter it is still in the car and never hurt anything so go figgure,. both are moser rear ends. and yes my gears do make noise.
I ran a 12 bolt in my car (33 spline axles) Ive cut 1.3x 60s on it wheels up almost every launch and never had a problem or increased noise. If the rear is set up correct you will not have any problems
The nine inch can explode worse than a twelve bolt.. Ive seen the pumpkin twist out and back side flex. I like the 12bolt because its a little more efficient to drive than the nine. If I upgrade, Im going with a dana 60.
