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GM 12 Bolt Posi-Trac 3.73 Gears

V-6 Camaros rule!
Posts: 61
Joined: 02/09
Posted: 11/13/13 12:10 PM

What type of power can a GM 12 Bolt Posi-Trac with 3.73 gears on a 71 Chevelle using a Turbo 350 Transmission and Street/Strip Tires handle on the drag strip?

Stock U-Joints
Stock Drive Shaft
B&M Speed Shifter  

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V-6 Camaros rule!
Posts: 40
Joined: 03/12
Posted: 11/14/13 01:50 PM

sorta hard to say, a stock converter is a lot more forgiving than a high stall,
the initial torque on the rear end with a stock converter and 400 hp engine would
in my opinion be a lot easier on the components than the same hp and a 3000 stall
converter, the sudden lock up will for sure put way higher stress loads on the
everything so basically with a stock converter you may never ruin the 12 bolt
and with the stall you are pounding away at it every time you launch hard and
slowly but surely wearing it out and eventually breaking it, just my opinion  

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I mow my lawn and find Chevys
Posts: 2253
Joined: 07/08
Posted: 11/14/13 03:43 PM

A stock 12 bolt will handle a fair amount of power. They used to put them behind 454 BBs which were rated at 450hp and probably made more. If you are racing a lot I would put the rear cover cap support on it. I would think it could handle some decent launch's too. Probably down into the 1.50 60' range, depending on weight, launch rpm, and tire grip you should be fine. I broke Ford 9" rears in some of my drag cars. Crazy  One sounded like a stick of dynamite going off. So you can break anything if you put enough bite and power to it.  

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