Smokey, Like Mossback44 said, to test an open type rear you have to turn the wheel two complete rotations and count drive-shaft rotations to find your true ratio. Some people recommend 20 revolutions and divide the shaft rotations by 10 but I didn't see a difference with mine. The explorer 8.8 I used was 1.5 inches shorter from the center of the axle to the face of the pinion flange than the old rear. I also used 1.5 inch spacers on each side to center my wheels in the fenders. I may end up going to deeper dish wheels so that would would be fine without the spacers.............Tim