The differential is to allow the two half shafts to rotate at different speeds during the steering process of the car to meet the needs of the two driving wheels for unequal distance driving, so that the car can drive in a straight line and turn lightly.

At present, domestically-produced automobiles basically use differentials composed of planetary gears, half-shaft gears, planetary gear shafts (cross shafts or a direct shaft) and differential housings.

The two halves of the differential case are fastened together with bolts, the driven gear of the main reducer is bolted to the flange of the differential case, and the cross-shaped planetary gear shaft is installed on the opposite side of the joint surface of the differential case. In the circular hole, each shaft journal is sleeved with a straight-tooth bevel planetary gear with sliding bearings, and the left and right sides of the four planetary gears are meshed with a straight-tooth cone half-shaft gear. The axle journals of the half shaft gears are supported in the corresponding holes on the left and right sides of the differential case, and the inner splines are connected with the half shafts.

In cars below medium-sized, two planetary gears are used in the differential because the torque of driving the wheels is not large. The corresponding planetary gear shaft is a direct-selling shaft, and the differential case can be made into an integral case with a large window hole. Through the large window hole, the operation of disassembling and assembling the planetary gear and the side gear can be carried out.

The axle housing supports and protects the main reducer, the half shaft of the differential, etc., so that the relative position of the drive shaft is fixed. Together with the driven axle, it bears the weight of the car and bears various reaction forces and moments transmitted by the wheels.

The drive axle housing is generally composed of a final drive housing and a half-shaft sleeve. The inner part is used to install the final drive, differential, and half-shaft; the exterior is connected to the frame through a suspension, and the two ends are equipped with a brake bottom plate and Connect the wheels to bear various forces and moments from the suspension and the wheels.