Patent ID: 8556763

Claim:
A vehicle final reduction gear unit comprising: a prime mover generating a drive force; a drive shaft transmitting a drive force from the prime mover; a small reduction gear coupled to the drive shaft for rotation; a large reduction gear meshing with the small reduction gear for rotation; a differential mechanism transmitting a drive force from the large reduction gear to left and right axles; a differential case housing the differential mechanism; and a final-reduction-gear case provided closer to a vehicle body, and housing the small reduction gear, the large reduction gear, the differential mechanism and the differential case; wherein the vehicle final reduction gear unit further includes: a first friction brake occupying an area between the final-reduction-gear case which is a stationary body and the differential case which is a rotating body for applying a pressing force in an axial direction to generate a frictional force in order to put a brake on the differential case; and a second friction brake occupying an area between the differential case and the right axle, for applying a pressing force in the axial direction to generate a frictional force in order to use a rotational difference to put the differential mechanism into a lock state; wherein the second friction brake is placed within the radius of the first friction brake, wherein the first friction brake comprises: a cylinder-shaped first friction brake supporter that is mounted to the differential case and extends from one of left and right ends of the differential case in the vehicle-transverse direction; a plurality of stationary friction discs that are spline-fitted into a cylinder-shaped inner peripheral surface of the final-reduction-gear case and able to move in an axial direction; and a plurality of first rotation friction discs that are spline-fitted into a cylinder-shaped outer peripheral surface of the first friction brake supporter and arranged alternately with the stationary friction discs; and the second friction brake comprises: a plurality of second rotation friction discs that are spline-fitted into a cylinder-shaped inner peripheral surface of the first friction brake supporter; a collar that is spline-fitted into the right axle; and a plurality of axle-side friction discs that are spline-fitted into a cylinder-shaped outer peripheral surface of the collar and arranged alternately with the second rotation friction discs.