FINAL DRIVE AND DIFFERENTIAL
An automatic or manual transmission transmits power by means of a rotating shaft to a final drive and differential unit. This unit, in turn, delivers power by means of two output shafts--one leading to each drive wheel.
The final drive provides an additional reduction. In a transaxle, the final drive is usually a set of planetary gears. In a car with rear-wheel drive and a front-mounted engine and transmission, the final drive is a set of bevel gears. The bevel gears mesh at a right angle. One gear is connected to the drive shaft; the other, to the differential.
The differential is a complex gear set that divides torque evenly between the two drive wheels. The differential also enables one wheel to rotate faster than the other. For example, when a car goes around a corner, the outside wheel must travel farther than the inside one. The differential enables the outside wheel to rotate faster than the inside wheel to cover the longer distance in the same time.
