Rear End Ratios

Longgone said

Once the car is jacked up, make a mark on both tires at 12 o`clock and another on the side of the driveshaft. Now rotate the wheel while you watch the driveshaft. Count the revolutions the driveshaft rotates for one rotation of the wheels. That will be the approximate gear ratio.

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Assuming it is a posi, those procedures are correct.

If it is an open, only jack one side and leave the other tire on the ground. Rotate the tire, on the jacked side, one full revolution, counting the revolutions and partial revolutions of the driveshaft, double that amount, and that is your gear ratio.

So, for example if you counted 1 3/4 turns, you have a 3.55.