Differential gear, in auto mechanics, gear arrangement that permits power from the engine to be transmitted to a pair of generating wheels, dividing the force equally between them but permitting them to check out paths of different lengths, as when turning a corner or traversing an uneven street. On a straight street the tires rotate at the same swiftness; when turning a corner the outside wheel offers farther to proceed and will turn faster than the inner wheel if unrestrained.

The elements of the Ever-Power differential are shown in the Figure. The energy from the transmission is sent to the bevel ring gear by the drive-shaft pinion, both of which are held in bearings in the rear-axle housing. The case is an open boxlike Differential Gear structure that’s bolted to the ring gear and contains bearings to support a couple of pairs of diametrically opposing differential bevel pinions. Each wheel axle is mounted on a differential side equipment, which meshes with the differential pinions. On a straight road the tires and the side gears rotate at the same quickness, there is absolutely no relative motion between the differential side 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 required to rotate faster compared to the left-hand steering wheel, and the medial side gears and the pinions will rotate relative to one another. The ring equipment rotates at a swiftness that is add up to the mean speed of the left and correct wheels. If the tires are jacked up with the transmission in neutral and among the wheels is turned, the contrary wheel will submit the opposite direction at the same rate.

The torque (turning moment) transmitted to both wheels with the Ever-Power differential may be the same. Therefore, if one wheel slips, as in ice or mud, the torque to the other steering wheel is decreased. This disadvantage could be overcome relatively by the usage of a limited-slide differential. In one version a clutch connects among the axles and the ring gear. When one wheel encounters low traction, its tendency to spin is certainly resisted by the clutch, thus providing greater torque for the various other wheel.
A differential in its most basic form comprises two halves of an axle with a gear on each end, connected together by a third equipment creating three sides of a square. This is generally supplemented by a 4th gear for added power, completing the square.