[kda2000]

What Outfield said. A little more info, normally when both wheels move (as the drive shaft moves the truck), for a 4.10 gear set the yoke will go around 4.10 times per full revolution of the tires. When one wheel on the ground (and one jacked up) then the motion on the yoke that is normally split between the two wheels all goes to the one that moves, and so the one wheel moves twice as far as it normally would. So to figure out what ratio you have, you spin the tire and count the revolutions of the yoke and multiple by two. To be a little more precise, mark the tire and spin it 10 times, count the turns on the yoke, and then multiple by two and divide by 10, and then you will get the integer number and the first digit behind the decimal point with precise accuracy. For example if you have 4.56 gears, and you spin the tire 10 times, the yoke should go around 22 1/2 time. So 22.5 *2 = 45; and 45 / 10 = 4.5 (the first two digits of 4.56 gears). This works for any gear ratio. Hope this helps.