PURPOSE: To provide a sufficient differential limit force by providing a friction clutch engaged by receiving the engaging thrust force of a first helical pinion gear when a differential case is rotated to one side and that of a second helical pinion gear when the differential case is rotated to the other.

CONSTITUTION: During running forward of a vehicle, a pinion gear 73 is moved to the left, a multidisc clutch 59 is pressed by a protrusion part 83, and a pinion gear 75 is moved to the right to press the antislip plate 37 of a differential case 21, and frictional resistance is generated. During the reversing of a vehicle, the pinion gear 75 is moved to the left, the multidisc clutch 59 is pressed through a press pin 89 and the pinon gear 73 is moved to the right, and the antislip plate 37 of the differential case 21 is pressed to generate frictional resistance. Since one set of the multidisc clutches 59 can be pressed by the helical pinion gears 73 and 75, the multidisc clutch 59 is pressed by one of the pinion gears 73 and 75 regardless of the advancing direction of a vehicle and a high differential limit function is provided.