The drive train is generally composed of clutches, transmissions, universal transmissions, final drives, differentials, and axle shafts. Its basic function is to transmit the power generated by the engine to the driving wheels of the car and generate driving force so that the car can run at a certain speed.

For front-and-rear vehicles, the torque from the engine passes through the clutch, transmission, universal joint, transmission shaft, main reducer, differential, and axles to the rear wheels, so the rear wheel is also called Drive wheel. The torque generated by the drive wheel gives a backward force to the ground and therefore causes the ground to produce a forward reaction force to the drive wheel. This reaction force is the driving force of the car. The front wheels of the car and the drive train generally have no direct power connection and are therefore called driven wheels.

The composition and layout of the drive train vary with the type of engine, the installation location, and the use of the car. For example, off-road vehicles mostly use four-wheel drive, so the assembly of transmissions and the like is added to its drive train. For front-drive vehicles, there are no drive shafts or other devices in their drive trains.