In front and rear wheel drive (or all-wheel drive) cars, due to the deformation of the suspension in the process of movement, the input shaft of the main drive shaft reducer and the output shaft of the transmission (or transmission box) often have relative movement. In addition, in order to effectively avoid some institutions or devices (can not achieve linear transmission), there must be a device to achieve normal power transmission, so the universal linkage transmission came into being. A universal joint transmission must have the following characteristics:

1. Ensure that when the relative position of the two connected axes changes within the expected range, the power can be delivered reliably;

2. Ensure that the two axes connected can run evenly. The additional load, vibration and noise caused by the Angle of the universal joint should be within the allowable range.

High transmission efficiency, long service life, simple structure, convenient manufacture, convenient maintenance. For the automobile, because the output shaft of the cross-shaft universal joint has a different rotation speed (certain Angle) compared with the input shaft, it is necessary to use double universal joints (or multiple universal joints) to drive. The two universal joints connected with the drive shaft are arranged in the same plane, and the angles of the two universal joints are equal. This is very important. In the design, the Angle of the universal joint should be reduced as far as possible.