the epicyclic gear mounted in the driving axle of a road vehicle that permits one driving wheel to rotate faster than the other, as when cornering
differential gear in American English
or differential gearing
a certain arrangement of gears (epicyclic train) connecting two axles in the same line and dividing the driving force between them, but allowing one axle to turn faster than the other: it is used in the driving axles of automobiles to permit a difference in axle speeds when making turns