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Old 12-05-2005, 07:47 PM
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help deciding rear gear

Trying to decide what gear to run in my 70 chevelle. It has a 496ci that makes avg 576lb ft tq 3K - 5K and 520hp @ 5300 with a TH400 trans to a 12 bolt. It will be a 60/40 Street/Strip and only plan to get on the higway when theres a car show nearby. What would be the optimal gear for this 3800lb car? I'm thinking 3:55 over the 3:73 and 4:10's are out of the question or can I go even lower than the 3:55's with that much torque down low?

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Old 12-06-2005, 10:30 PM
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Do you have a stall converter? If so what RPM is it based on?
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Old 12-07-2005, 06:09 AM
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There is little differance between a 3:55 and a 3:73 (probably a couple hunderd rpm's at highway speed) , personally I would go with the 3:73.

Vince
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Old 12-07-2005, 04:03 PM
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No I havent purchased my converter yet that was my next question. I was looking at the coan converters and emailed the techs yesterday havent got a reply yet. What do you recommend for the 3:73's? If I were to choose the 3:73's over the 3:55's how much would I lose on my E.T. at the strip?
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Old 12-07-2005, 04:19 PM
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i may be wrong, but i think you would be faster , at least out of the hole, with 373
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Old 12-07-2005, 04:24 PM
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Quote:
Originally Posted by Derkyb
It has a 496ci that makes avg 576lb ft tq 3K - 5K and 520hp @ 5300 with a TH400 trans to a 12 bolt. It will be a 60/40 Street/Strip and only plan to get on the higway when theres a car show nearby.
With that much Horsepower and torque........you will NEED some big tires to hook it all up. Big tires are LARGE tires....so a 4.10 with a tall tire is like a 3.55 with a smaller tire....I would go 30 to 31 inches tall on the tires and run at least a 4.10
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Old 12-07-2005, 04:28 PM
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When I suggest a gear ratio for a race car, it is totally dependant on the MPH through the traps. Of course tire size makes a big difference on that decision. The first question that you have to ask yourself is if you want to focus on the track performance or the streetability of the car. What is the tire size, and weight of the car. I can give you a ballpark MPH for the 1/4, then you could see what the optimum gear ratio would be for the car. It may not be too far out of range for what is practical on the street.

If you would like to know about a converter, we need a little more info: Are you using a transbrake? Cam specs (lift, duration @ .050)? Max RPM that you are going to turn the motor? I would be glad to give you a suggestion as to what I think would be appropriate for the car.
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Old 12-07-2005, 04:35 PM
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Good point Deuce, Its goona be tough getting that much torque to the ground. I was thinking with a 3:55's it would help control tire spin out of the hole. Plan on running those new mickey et/streets on a 15 in rim 275 some guys are going 9's on these tires so I know it can be done.

My cam is a comp 292 244in/ex@50 550 lift not going to run a trans break and probaly will not spin the motor past 5700.
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