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Old 07-27-2012, 02:24 AM
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Posi or not

I'm close to getting my GP on the streets and would like to know the benefits of changing the gear ratio and converting to Posi traction. I have a 455 bored 30 over, rebuilt th400 trans with B&M hole shot 2500 stall with a shift kit installed also. I want this car to be a street crusier. I might take it to the track once or twice just to see it run. What Gear should I run?
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Old 07-27-2012, 06:11 AM
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3.42 or 3.55 would be good all around. If you are going to be on the highway you should probalby stay away from the 3.73 because your RPMs at 60 and 70 MPH will probably be higher than you want. If you will be on the highway a lot then you might want to look into a 3.08 or 3.31. Going to a 3.73 would make it accellerate quicker, but cost you on the highway.

Adding a posi (limited slip differential) will get both wheels pulling instead of just one. You don't get anywhere very quick when you are spinning one wheel.
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Old 07-27-2012, 06:29 AM
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Yes put in a posi,you will be happy you did,just use a newer one,something without clutchs.I used the OME posi out of a 79 Trans Am it has clutchs in it it works fine for now but I should of used a clutch less design.Far as rear gears that all depends on if you want to hear your engine turning 3 grand at 70mph,like mine use to,I had 3.42s & a Th350.I kepted the 3.42s but put in a 700r4,it droped the rpms by 1000.I wouldnt go any lower than 3.42s if you want a good lanch.
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Old 07-27-2012, 06:55 AM
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Anybody experts on what Pontiac Used in their rears? I need to know the diameter of the ring gear.
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Old 07-27-2012, 06:59 AM
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Some of the GPs had the 8.2 BOP 10 bolt and some had the Chevy 12 bolt. You will need to check and see which one you have. I recommend the Eaton Posi for either one of these. This is a very good differential and it is rebuildable. The Yukon Dura Grip is also very good. Randy's Ring & Pinion has them for both of these rear ends. You can also check with Jim at www.jdrace.com
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