The axle is one of the key components of the vehicle chassis, which is directly related to the operation efficiency of the vehicle. In terms of classification, the axle can be divided into four categories: drive axle, steering axle, steering drive axle and support axle. Among them, steering axle and supporting axle (also called trailer axle or trailer axle) are driven axle without drive shaft; The structure of the drive axle and steering drive axle is more complex, which needs to bear the power transmission of the vehicle.

The common drive axle is mainly composed of the main reducer, differential, half shaft, drive axle housing and other components. The specific functions can be divided into the following four points:

1. The engine torque transmitted from the universal transmission device is transmitted to the wheels through the main reducer, differential, half shaft and hub to reduce the speed and increase the torque;

2. Changing the torque transmission direction through the bevel gear pair of the main reducer;

3. The differential function of the wheels on both sides is realized through the differential to ensure that the inner and outer wheels turn at different speeds;

4. Through the axle housing and wheels, the load bearing and force transmission functions are realized.

The single stage reduction axle and double stage reduction axle, as we often say, are typical drive axles, but there are many differences between the two types of axles in structure and performance.

The axle shaft bridge is light in weight, convenient in maintenance, and suitable for standard load transportation on highways

Single stage reduction axle, commonly known as half axle axle, is also called "big belly axle" by many car owners due to its large differential housing.

From the perspective of structure, the axle shaft bridge is mainly composed of a driving bevel gear (commonly known as angle gear) and a driven bevel gear (commonly known as basin gear). It is simple in structure, lighter in weight, lower in failure rate, and more convenient in maintenance.

However, the torque amplification effect of the axle shaft bridge is not outstanding. Because the gear diameter of the main reducer is relatively large, and the volume of the axle housing is also large, the ground clearance of the vehicle is small, which affects the trafficability of the vehicle. Especially when the road conditions are poor, the disadvantages of the axle shaft bridge are more obvious.

These characteristics make the axle shaft bridge more suitable for use in good working conditions, such as standard load transportation, high-speed transportation and other vehicles with relatively flat road conditions and mainly standardized transportation. It not only has excellent lightweight performance, but also has low fuel consumption, and can effectively prevent the high temperature phenomenon caused by long-term high-speed driving of the axle head. The common single-stage reduction axle models are 435, 440, 457, 459, 460, 469, etc.

The two-stage reduction axle has strong power and good trafficability, and is suitable for complex road conditions

The two-stage reduction axle, also known as wheel side axle or wheel reducer axle, has a group of reduction drives at the wheel side compared with the axle shaft axle. The torque amplified by two stages is transmitted to the wheels, and the driving force is very strong. At the same time, the diameter of the basin teeth of the main reducer of the wheel side axle is reduced, the volume of the axle housing is significantly smaller, and the ground clearance of the vehicle is large enough to ensure good trafficability.

However, the more complex structure not only affects the transmission efficiency, but also has higher technical requirements for assembly and maintenance, which is more fuel consuming. When the vehicle is running at a high speed, the wheel reducer undertakes most of the tasks of speed change and torque increase, so the heat generated by the friction between the tire and the ground is easily concentrated at the wheel end, resulting in poor heat dissipation conditions, which is not suitable for long time and long distance driving.

In contrast, wheel side bridges are more suitable for low-speed and heavy load transportation under complex working conditions, such as construction sites, unpaved roads and muddy roads. Their strong driving force and high trafficability can provide stronger difficulty relief capability, and they are more durable.

To sum up, the semi axle bridge is suitable for standardized highway logistics transportation and transportation conditions with good road conditions and small load capacity; Wheel side bridges are more suitable for construction vehicles with poor road conditions, more climbing and heavy loads. Although the two axles are both drive axles, the car owner should consider the actual use needs when selecting them.