Mark a axle and turn the pinion. See how many turns the pinion takes to complete one revolution of the axle. It will get you close.
Number of Turns Approximate Gear Ratio
2 - 3/4 2.72:1 or 2.77:1
3 - 0 3.07:1
3 - 1/2 3.54:1
3 - 3/4 3.73:1
4 - 0 4.10:1
4 - 1/2 4.56:1
4 - 3/4 4.88:1
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Frank
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