coupling China DIFFERENTIAL gear, in automotive mechanics, gear arrangement that allows power from the engine to be transmitted to a couple of traveling 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 speed; when turning a corner the outside wheel provides farther to proceed and will turn faster than the inner wheel if unrestrained.
The elements of the Ever-Power differential are demonstrated in the Figure. The power from the transmission is sent to the bevel band equipment by the drive-shaft pinion, both which are kept in bearings in the rear-axle casing. The case is an open boxlike framework that's bolted to the ring gear and contains bearings to support one or two pairs of diametrically opposite differential bevel pinions. Each wheel axle is mounted on a differential side gear, which meshes with the differential pinions. On a directly road the wheels and the medial side gears rotate at the same quickness, there is absolutely no relative motion between your differential part gears and pinions, plus they all rotate as a device with the case and ring gear. If the vehicle turns to the left, the right-hand wheel will be forced to rotate faster than the left-hand steering wheel, and the medial side gears and the pinions will rotate relative to one another. The ring gear rotates at a quickness that is add up to the mean speed of the remaining and right wheels. If the wheels are jacked up with the tranny in neutral and among the wheels is turned, the opposite wheel will submit the opposite direction at the same quickness.
The torque (turning moment) transmitted to the two wheels with the Ever-Power differential is the same. Therefore, if one steering wheel slips, as in ice or mud, the torque to the other wheel is reduced. This disadvantage can be overcome relatively by the utilization of a limited-slip differential. In one edition a clutch connects among the axles and the ring gear. When one steering wheel encounters low traction, its tendency to spin is usually resisted by the clutch, thus providing greater torque for the additional wheel.
OPEN DIFFERENTIAL:
A differential in its most basic form comprises two halves of an axle with a gear on each end, linked jointly by a third gear creating three sides of a sq .. This is generally supplemented by a 4th gear for added strength, completing the square.