DIFFERENTIAL UNITS

When a car turns a corner, one wheel is on the “inside” of a turning arc, and the other wheel is on the “outside.” Consequently, the outside wheel has to turn faster than the inside one in order to cover the greater distance in the same amount of time. Thus, because the two wheels are not driven with the same speed, a differential is necessary. A car differential is placed halfway between the driving wheels, on either the front, rear, or both axes (depending on whether it’s a front-, rear-, or 4-wheel-drive car). In rear-wheel drive cars, the differential converts rotational motion of the transmission shaft which lies parallel to the car’s motion to rotational motion of the half-shafts (on the ends of which are the wheels), which lie perpendicular to the car’s motion.