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Old 10-16-2006, 05:27 PM
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GM 12 Bolt Whats going to break first?

Hello Everyone,

I have a stock GM Car 12 Bolt Posi rear end and was wondering what are the weak links? I have it in my 58 Chevy PU, Cal Tracs, Nitto Drag Radials, 2500rpm stall 383 stroker with 420hp + 120 NOS.

A few months ago I changed the oil in it and it looked like it had been neglected, really dirty and a few small chunks of gear. I figure it will have to be rebuilt sooner or later so I just wanted to know what to expect.


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Old 10-16-2006, 05:43 PM
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I've got a 12 bolt truck rear in my vega drag car. When we had the stock rear in it with 450 hp the spider gears were going like clock work as well as the bolts on the ring gear when we had a spacer in it because of the small or lower gear carrier. Actually spit the ring gear right out the back of the housing one time right though the rear cover.I now have a spool with a heavy aluminum cover and it holds up rather well.
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Spider gears. I could not keep them together. No matter what brand.
Big block, 4-speed, heavy car, big slicks.
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Old 10-17-2006, 08:23 AM
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I used to have a 12 bolt and it eat spider gears and axles. Put a spool, big axles and bearing caps on it and never had anymore problems.
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Old 10-17-2006, 09:23 AM
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At that power level I think they'll be fine, but I'd consider a c-clip eliminator just for peace of mind.
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Old 10-17-2006, 05:45 PM
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I have a 87 10 bolt with a power trax locker and 4.56 gears with a 700r4 behind a 500+hp 427 in my 58 Apache so far no problem.I rebuilt the rearend before I installed it because the spider gears were on there way out.The 12 bolt axles are much stronger.I would expect it to hold up fine.Like all Chevy's the axle bearing is the weak spot but shouldn't be an issue unless you haul a lot of weight or a big trailer
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