The grooves made by the needle roller bearings on the trunnion of the cross are known as brinelling. Brinelling can also be caused by too much torque for the capacity of the U-joint used. End galling is a displacement of metal at the end of the trunnion and can also be related to angularity problems. Both of these problems can be caused by failure or lack of lubrication. Fractured parts caused by torque, fatigue and bending are associated with overload, excessively high U-joint angles and driveline lengths exceeding critical speed limitations.
Vibration is a driveline problem that can either transverse or torsional.
Transverse vibration is the result of unbalance acting on the supporting shafts as the driveline rotates. The faster the shaft turns, the greater the unbalance force acting on the shaft. As the supporting members have a natural frequency of vibration similar to a swinging pendulum, a violent vibration may exist at certain periods when the speed of rotation and the natural frequency of supports coincide. Each end of the shaft must be balanced individually as each support is responsive to an out of balance condition in portion of the shaft it supports. Transverse vibration caused by a driveline out-of balance will usually emit sound waves that you can hear and mechanical shaking that you can feel.