Re: 72 Saginaw 3 speed Speedo Drive gear?
With your current size tires;
If you go to the 21T gear your spedomete3r will be off by 2.3% fast.
If you go to the 22T gear your spedomete3r will be off by 2.32% slow
You should have the smaller of the two 8T gears. (The 1.76" OD gear).
I get a 7% difference, in speed, using 55/59mph and your existing tire size and the 8/21T gear? Almost three times the what the calculated speed difference should be. Go figure.
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