The car transmission (Transmission) has several functions:
1. Change the transmission ratio, expand the driving torque and speed of the change range to adapt to the frequent changes in driving conditions, while the engine in favor of the high power and low fuel consumption of the working conditions;
2. In the direction of the engine rotation is unchanged, so that the car can be backward driving;
3. The use of Air block, interrupt power transmission to the engine can start, speed, and facilitate transmission shift or power output.
4. Transmission is composed of variable speed transmission mechanism and control mechanism, and can be fitted with power output when needed. There are two ways to classify: according to the change of transmission ratio and according to the different ways of operation.