RPM Drop Between Gearbox Ratios

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Jerry Poole
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RPM Drop Between Gearbox Ratios

Post by Jerry Poole » Sun Feb 01, 2015 5:06 am

Could anyone from the forum please direct me to a site or formula that calculates the RPM Drop that would occur with different gearbox ratios ? I have a gearbox, 5 speed , that allows me to change ratios for each forward speed and would like to know what the RPM Drop that would occur with each ratio change at any RPM. Thanks for any information and input. Jerry

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MadBill
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Re: RPM Drop Between Gearbox Ratios

Post by MadBill » Thu Apr 23, 2015 9:32 pm

Long time coming, but the answer is pretty simple: multiply the shift RPM by the gear ratio you're shifting into and divide the result by the ratio of the gear you're shifting out of. E.g., if 3rd gear is a 1.5:1 reduction and 4th is 1.2 and you shift into the latter at 8,000 RPM, the revs after the shift will be (1.2 x 8000)÷ 1.5 = 6400.

In many applications, it is found best for each 'split' to be smaller than the previous one, e.g., 1-2 gives 5800 RPM after the shift, 2-3 = 6100, 3-4 = 6400, 4-5 = 6700...
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Kenova
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Re: RPM Drop Between Gearbox Ratios

Post by Kenova » Thu Apr 23, 2015 9:33 pm

Over the hill but still learning!
Retaining it is the hard part.

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John Wallace
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Re: RPM Drop Between Gearbox Ratios

Post by John Wallace » Sat Apr 25, 2015 8:09 am

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