This method was contributed by member: theonlybull

What I do, is jack one tire up, mark it, then mark the driveshaft. Now one person turns the one rear tire 20 times, and the other person counts the driveshaft rotations. Then divide the resulting turns of the driveshaft by 10. If you count 35, then you have 3.50 gears..

Doing it this way will let you tell the difference between 3.00, and 3.10 gears.