Worn Bearings inside a Universal Joint – The joint contains 4 small bearings at the end of each of the cross, these bearings need to be maintained and kept lubricated or they will heat up and seize, requiring replacement meaning time and money, add to that the universal joint design which allows the two attached shafts to work out of alignment. This misalignment means the ball bearings inside the bearings will wear against the outside of the race (groove the ball bearings sit in) leading to the race being enlarged and the ball bearings becoming loose, leading to increase vibration potentially damaging attached equipment or bearing failure.