Diff Gears & Wheel Diam Equations

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Apr 15, 2008 | 12:13 AM

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From: Northern New Mexico

Diff Gears & Wheel Diam Equations

I am attempting to evaluate the gearing on the 1964 F500 that is the subject of a few other threads. Is it possible to equate the gearing and wheel diameter of this truck with say an F250 with 33 inch tire diameter and 4.11 grearing? The auto math concept is called "Replacement Ratio" I think. My truck as 6.20 gearing and 37 inch diameter wheels. I am trying to determine if the current gearing is "low" like a 4.11 or 4.56 in a truck with 16 inch wheels or what some might call "normal general purpose gearing."

Hopefully, this makes sense. It is hard to express in words and i do not know the equations.

Thanks.

Apr 15, 2008 | 10:34 AM

subs1000w

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yes even with 37in tires 6.20 gearing is still low you could get away with gearing in the 4s like 4.11 or 4.56

Apr 15, 2008 | 10:53 AM

85e150

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37 inch tires, 6.20 axle, 60 mph = 3378 rpm.

Scroll down to the second calculator at this site. Use 1:1 for transfer case, as you don't have one.

Novak Conversions - Gearing & Gearing Math for Jeeps

Apr 16, 2008 | 08:05 AM

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From: Northern New Mexico

Thank you both very much. That link is exactly the kind of refence tool I need for this and four other trucks.

subs1000w (you must be an electrician?) It seemed like this was geared low. I can see now that 6.20 is real low for a road truck.

It has the same final ratio as my 1942 Chevy 1.5 ton 4 X4 which struggles along powered by a 235 I6.

THanks again for the advice and help.