Differential gear, in auto mechanics, gear arrangement that allows power from the engine to be transmitted to a pair of driving 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 road. On a straight street the tires rotate at the same velocity; when turning a part the outside wheel provides farther to go and can turn faster compared to 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 band gear by the drive-shaft pinion, both which are held in bearings in the rear-axle casing. The case is an open boxlike coupling China framework that is bolted to the ring gear and contains bearings to support a couple of pairs of diametrically reverse 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 tires and the side gears rotate at the 
same speed, there is no relative motion between your differential aspect gears and pinions, and they all rotate as a unit with the case and ring gear. If the automobile turns left, the right-hand wheel will be required to rotate faster than the left-hand steering wheel, and the medial side gears and the pinions will rotate relative to each other. The ring equipment rotates at a acceleration that is add up to the mean rate of the left and right wheels. If the tires are jacked up with the transmission in neutral and one of the wheels is turned, the contrary wheel will submit the opposite direction at the same quickness.
The torque (turning moment) transmitted to the two wheels with the Ever-Power differential may be the same. Consequently, if one wheel slips, as in ice or mud, the torque to the other steering wheel is reduced. This disadvantage can be overcome somewhat by the use of a limited-slide differential. In one edition a clutch connects one of the axles and the band gear. When one steering wheel encounters low traction, its tendency to spin can be resisted by the clutch, thus providing better torque for the various other wheel.
OPEN DIFFERENTIAL:
A differential in its most basic form comprises two halves of an axle with a gear on each end, connected jointly by a third gear making up three sides of a sq .. This is usually supplemented by a 4th gear for added power, completing the square.