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mars77 09-14-2009 07:41 AM

Change gear ratio on rear end?
Is it possible to change a rear end from one gear ratio to another?

If so, what is a recommended gear ratio for a Chevy BB 454 with around 400-450 HP, rebuilt and enforced TH350 with a converter at around 2200? The car is used 95% as a daily driver but as it is know is is not very a good idea to drive it on the highway (100 KPH at 3200RPM) and a pretty lousy gas milage of 3 liters/10 kilometers.

Today I have a 10 bolt rear end with a for the moment unknown gear ratio.

Thanks in advance!


Barn Owl 09-14-2009 09:04 AM

Yes it is possible. You first should figure out what gear you have in there currently, and change accordingly. the TH350 does not have an overdrive and even if you change the rear to a relatively high gear the tranny will still be winding at a high rev at highway speed and you will sacrifice low end torque. More involved addition to changing the final drive, a gear vendor overdrive or a 700r4 or 2004r would also be a nice upgrade if you are using it mostly for a DD.

SSedan64 09-14-2009 12:27 PM

Here's a Gear/Rpm calculator you can use to see what gear would work well. Go down to the 2nd calculator and input some numbers. It's in MPH but, you can convert to KPH. >>

MPH X 1.609 = KPH
KPH X .621 = MPH
Inch X 25.4 = MM.
MM X .0394 = Inch
Sounds like you have about a 3.73 gear, if your rear tire is 26" Dia.
A 3.08 gear would give you 100KPH at 2500rpm.

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