An improvement is provided in a differential gear which includes an input shaft, a differential casing adapted to be rotated by the input shaft, a differential pinion shaft radially extending within the differential casing and a plurality of differential pinion gears rotatably mounted on the differential pinion shaft. A pair of side gears having a rotation axis common to that of the differential casing and meshing with the pinion gears, and a pair of output shafts fixed to the side gears. The improvement comprises a centrifugal weight member slidably mounted on the differential pinion shaft and radially inwardly biased, and a multiple disc clutch provided between the differential casing and the output shafts. The clutch is adapted to be engaged in response to the radially outward movement of the centrifugal weight member.