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I think i am in the right forum, please don't get mad if im not.
Alright, so i have a 77 sedan deville with a built up(hot cam, high compression heads & pistons, forged rods, aluminum intake, 870 cfm carb ect...) caddy 500 motor. I currently have the stock th400 trans in just so i can run it around and break in the motor, soon ill swap it out with a tremec TKO600 5-speed trans. So the big question is what rear(brand and ratio) should i use that is also a posi? i would like to keep the housing and just replace the pumpkin guts if possible. Any and all suggestions would be helpful.
 

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95 FWB 81SDV 96 FWB 94 Fleetwood
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You will be better off building another th400 with all the best parts.. standards have a hard time standing up to the torque of the 500...For a rear , I think a 3.08 is a good ratio for the 500...a 77-79 limo has a 3.08 gear with 33 spline axles... Or a 96 or earlier chev cop car has a rear that will bolt in...not sure of there gear ratio...
 
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Depends on what you’re looking for. You can do a search and find numerous tire size gear ratio calculators for drag racing.
 

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94 ETC,97 STS
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500's have prodigious torque and don't have to run high rpm's so the 3.08's would be a good choice.

I had a couple of 5.0 Mustangs. They ran 2.76's with the 5spd.
 
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