How do you figure final drive gear ratio?

To calculate the final drive gear ratio, divide the number of teeth on the driven gear (typically the ring gear in the differential) by the number of teeth on the driving gear (usually the pinion gear). For example, if the ring gear has 40 teeth and the pinion gear has 10 teeth, the final drive gear ratio would be 40:10, which simplifies to 4:1. This ratio indicates how many times the driveshaft must rotate to turn the wheels once, influencing acceleration and top speed.