Among the universal joint mating, a parts (output shaft) around its own axis of rotation is driven by another component gimbal (Input shaft) around its axis of the rotational.
The cardan joint is also called universal joints or gimbal, it is a part which can able variable angle power transmission. It is also use for the need to change the position of the drive shaft line direction. And it becomes the "joint" of the vehicle drive system of the universal transmission. Universal joint and drive shaft combination, known as the gimbal transmission.
The structure and the action of the gimbal somewhat like the human limbs on the joint, which allows the angle changes in a certain range between the parts to be connected. To meet the power transmission, adaptation to changes in the angle caused by the vertical runout is generated when the steering and the car running, it is common connected to the u-joint at the drive axle of a car before drive and between the half shaft and the wheel. However, due to the limitation of the axial dimension, the requirements of declination is larger relatively, so it is hard to make the instantaneous angular velocity equal of the output shaft and the shaft into the shaft only by a single u-joint, in this case, it is likely to cause vibration, exacerbate damage to the components, and generates a lot of noise.
And therefore, all kinds of CVJ are widely used. Front drive vehicle, each axle with two CVJ. It is the axle inner u-joint which is close to the transaxle gimbal, and the half axle outer universal joint is close to the axle. On a rear drive vehicle, as a whole, the engine, clutch and gearbox are installed in the vehicle chassis, and the drive axle connected by elastic suspension and the frame, there is a distance between the two, and they need to be connected. Not only the car beating which produce by the uneven pavement and load change, but also the potentiometer of these two assemblys installed, will make the angle and distance between the gear output box shaft and drive axle main reducer input shaft changed.