Automotive transmissions are classified into hydraulic automatic transmissions (AT), mechanically continuously variable automatic transmissions (CVT), electronically controlled mechanical automatic transmissions (AMT), and dual clutch transmissions (DSG).

1. AT is composed of a hydraulic torque converter, planetary gears and a hydraulic control system. The transmission torque is realized through a combination of hydraulic transmission and gears. Among them, the hydraulic torque converter is the most important component. It consists of a pump wheel, a turbine wheel and a guide wheel, and has the functions of transmitting torque and clutch.

2. Compared with AT, CVT eliminates the need for complicated and bulky gear combination transmission, but the transmission uses two sets of pulleys. The speed change is achieved by changing the contact radius between the driving wheel and the driven wheel belt. Because the gear transmission is cancelled, the transmission ratio can be changed at will, the speed change is more stable, and there is no sudden shift.

3. AMT is a stepped automatic transmission like the hydraulic automatic transmission (AT). On the basis of the ordinary manual transmission, a microcomputer-controlled electric device is added, which replaces the manual operation of clutch disengagement, engagement, transmission selection and shift action, and realizes automatic shifting.

4. DSG gearbox is obviously different from traditional automatic gearbox. DSG did not use hydraulic torque converter from the beginning. This transmission is not produced on the basis of the traditional automatic transmission concept. The engineers who designed DSG embarked on an innovative new technology path, cleverly combining the flexibility of a manual transmission with the convenience of a traditional automatic transmission.