Its says the gear ratio in a set of numbers on the ring, or the shaft of the pinion. It will be the number of teeth on each... For example, the gearset I have been staring at lately is a 3.73 in my ZJ... On the ring gear, it has 41 11 next to each other, a little set off from the part number... 41 teeth on the ring, 11 on the pinion. Divide 41 by 11, and you get 3.727, which is rounded up to 3.73.
Rob L.