Differential gear, in auto mechanics, gear arrangement that permits power from the engine to be transmitted to a set of generating wheels, dividing the force equally between them but permitting them to follow paths of different lengths, as when turning a corner or traversing an uneven road. On a straight street the wheels rotate at the same rate; when turning a part the outside wheel has farther to move and will turn faster compared to the inner steering wheel if unrestrained.

The elements of the Ever-Power differential are demonstrated in the Figure. The power from the transmitting is delivered to the bevel band equipment by the drive-shaft pinion, both which are kept in bearings in the rear-axle housing. The case can be an open boxlike framework that’s bolted to the band gear and contains bearings to support one or two pairs of diametrically opposing differential bevel pinions. Each steering wheel axle is attached to a differential side equipment, which meshes with the differential pinions. On a directly road the wheels and the medial side gears rotate at the same acceleration, there is no relative motion between the differential part gears and pinions, and they all rotate as a unit with the case and ring gear. If the vehicle turns left, the right-hand wheel will be forced to rotate faster compared to the left-hand wheel, and the side gears and the pinions will rotate relative to each other. The ring gear rotates at a quickness that is add up to the mean acceleration of the left and correct wheels. If the tires are jacked up with the tranny in neutral and among the tires is turned, the opposite wheel will turn in the opposite direction at the same velocity.

The torque (turning instant) transmitted to both wheels with the Ever-Power differential is the same. Therefore, if one wheel slips, as in ice or mud, the torque to the other steering wheel is reduced. This disadvantage could be overcome relatively by the use of a limited-slip differential. In one edition a clutch connects one of the axles and the band gear. When one wheel encounters low traction, its tendency to spin is usually resisted by the clutch, therefore providing better torque for the other wheel.
A differential in its most basic form comprises two halves of an axle with a gear on each end, connected jointly by a third equipment making up three sides of a square. This is normally supplemented by a fourth gear for added strength, coupling China completing the square.