Start / Terms / Overall Gear Ratio
The overall gear ratio is the ratio of engine speed to drive wheel speed. It combines the gear ratios of the transmission, the differential, and, if you have one, the transfer case ratio.
For example, if the transmission gear ratio is 2.97:1 and the differential ratio is 3.7:1 then the overall gear ratio is 2.97 X 3.7 or 10.989:1. In this case, for one turn of the drive wheels the engine turns 10.989 times. And for one turn of the engine, the drive wheels turns 1/10.989 or 0.091 turns.