Deceleration: The main reducer assembly can reduce the input speed, which is achieved through the gear ratio. When the high-speed input shaft drives the gear to rotate, the speed of the output shaft will decrease accordingly. Increase torque: When the transmission speed is reduced by the main reducer, a higher output torque can be obtained, so that a greater driving force can be obtained. Change the power output direction: The main reducer assembly also has the function of changing the power output direction, which can realize the differential between the left and right wheels or the middle and rear axles. The output of the transmission is a torque that rotates about the longitudinal axis, and the wheels must rotate about the horizontal axis of the vehicle, so a device is needed to change the direction of power transmission. The main reducer assembly is to play such a role.