Two-stage speed changing main reducer assembly for vehicle

The invention provides a two-stage speed changing rear axle assembly for a vehicle. The two-stage speed changing rear axle assembly for the vehicle comprises a main reducer and a rear axle, wherein the rear axle comprises a first half shaft, a second half shaft, an axle rack, axle shells, brake drums, brake discs, inserting keys, reinforcing ribs, a shock absorber bearing and an oil tube card; the axle shells are arranged on two sides of the axle rack; the inserting keys are respectively arranged at one end of the first half shaft and one end of the second half shaft; the first half shaft and the second half shaft are connected with a left half shaft and a right half shaft which are arranged on two sides of a differential mechanism; the brake discs are respectively arranged at one end of the first half shaft and one end of the second half shaft; each brake disc is provided with the corresponding brake drum; each brake drum is connected with the corresponding brake plate through bolts; and a differential case of the main reducer is connected with a high-gear driven tooth, an intermediate-gear driven tooth and a low-gear driven tooth. The rear axle assembly is compact in structure and reliable in operation, and can be used with a speed changing box of an engine; a gear shifting and torque changing range of the motor vehicle can be expanded; the optimal running speed of the motor vehicle is increased obviously; the climbing ability of the motor vehicle is improved; and the service life of the two-stage speed changing rear axle assembly for the vehicle is long.