Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Rear end gear ratio change = spedo. cable gear change. help? turbo 350
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Old 07-18-2007, 10:54 AM
F&J F&J is offline
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Quote:
What is the best way to determine gear ratio?
Of what? the rear axle? If so, jack up one rear wheel on a non-posi car, put a mark on the tire and driveshaft. Then rotate the tire 2 exact turns whil counting how many turns on the driveshaft. If the shaft turns 3 & 3/4 turns, it's a 3.70 ish; if 2 & 3/4 it's around a 2.70 ish.

If it's a posi, jack up both wheels but only turn the tire one turn.

The old speedo should work. I ran a 30 DeSoto with a GM 4 speed trans. The fitting on the old speedo was the same as a more modern car. My old speedo was not a needle, rather a rotating dial.
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