gear ratio question?
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gear ratio question?
I have a 78 f250 sc with 4.11 axels. I plan on going to 38.5" tires which will put my new ratio to around 3.08. Do you all feel that is a deep enough gear for a 4x4 and for towing. I plan on rebuilding the engine with a butt load of torque but I have some concerns. What do you all think?
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There is a formula that you can use to find out what gear you need to get your truck back to it stock power. You take the size you want to go to and divide it by the old tire size. The you multiply that number by the gear you have now. The number is what gear you need to have your truck run the same.
Ex. (35inch/29inch)=1.206*3.73=4.50 gear or a 4.56
Ex. (35inch/29inch)=1.206*3.73=4.50 gear or a 4.56
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Yeah I know of the Calculation. I am more curious as to what people feel about a 3.08 final gear ratio. Should help the mpg but I'm not sure how it will do towing.
Thanks for the help.
Thanks for the help.
Last edited by Modified; Mar 2, 2006 at 08:04 PM. Reason: typo
Fleet Mechanic
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From: Hartford, AL
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Fleet Mechanic
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From: Hartford, AL
When I said I would personally go with the 3.50, I was referring to final ratio taking into tire size.
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Post Fiend
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From: Louisiana
Originally Posted by Modified
Yeah I know of the Calculation. I am more curious as to what people feel about a 3.08 final gear ratio. Should help the mpg but I'm not sure how it will do towing.
Thanks for the help.
Thanks for the help.
If you had the money, regear to about 4.88 or just put that money into the engine, and give it plenty of power in all parts of the power band, helping gas consumtion on acceleration w/ the 4.11s.
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From: Louisiana
Originally Posted by 73FOMO
When I said I would personally go with the 3.50, I was referring to final ratio taking into tire size.
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From: montana
what engine/trans?
depends on the engine trans combo. I run 4.10 gears in a 78 f-150, with 38.5 boggers, BUILT c-6, 514 ci engine. With this I pull as good as any diesel,(except mileage-ugh 6-ish). But with a mild 460 or 400m, Gear it to a 4.56 or 4.88.
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