The combination of universal joint and driveshaft, called universal joint transmission, is a very important part of the car. In a universal joint fit, the rotation of a component (output shaft) around its axis is driven by the rotation of another component (input shaft) around its axis. However, there are many types of universal joints. I don't know much about it or custom universal joints are simpler.
One of the rotating forks drives the other fork to rotate through the cross shaft, and at the same time, it can swing in any direction around the center of the cross shaft. The needle in the needle roller bearing can rotate on its own during rotation to reduce friction. The shaft connected with the input power is called the input shaft (also called the driving shaft), and the shaft output through the universal joint is called the output shaft (also called the driven shaft). When working with an angle between the input and output shafts, the angular velocities of the two shafts are not equal, which will cause the output shaft and the transmission components connected to it to produce torsional vibration and affect the life of these components. A universal joint that has no obvious elasticity in the torsion direction. It can be divided into non-constant velocity universal joints, quasi-constant velocity universal joints, and constant velocity universal joints. Variable speed universal joints. When the angle between the two shafts connected by the universal joint is greater than zero, the output shaft and the input shaft transmit motion at a variable instantaneous angular velocity ratio, but the average angular velocity is equal to the universal joint.
The above is the working principle of universal joints such as the universal joint for truck . xsjbearing.com