[robnolimit]

Jack the rear off the ground. Put a mark on the bottom of the tire, and the bottom of the driveshaft. turn the driveshaft, count the turns, until the tire makes one full revolution. You will have to estimate the last partial rotation of the driveshaft. 1/4 turn = .25, 1/3 turn = .33, 1/2 turn = .5 ......... This is not perfect, but will get you close. Common gear sets are - 3.31 - 3.54 - 3.70 - 3.90 - 4.10 - 4.33