Universal joint refers to the use of ball and other devices to achieve the shaft power output in different directions, it is also a very important part of the car. The combination of universal joint and transmission shaft is called universal joint transmission device. In the front engine rear-wheel drive vehicle, the universal joint transmission device is installed between the transmission output shaft and the drive axle main reducer input shaft; In front-engine, front-wheel-drive vehicles, the drive shaft is omitted and the universal joint is mounted between the front axle axle, which is responsible for both driving and steering, and the wheels.