What is the proper repair if a driveshaft universal joint (U-joint) is dry and loose?

When a driveshaft universal joint (U-joint) is dry and loose, the most effective repair is to replace the U-joint. This is because a dry U-joint indicates that the lubrication has failed, which can lead to wear and damage that cannot be adequately repaired by simply greasing or tightening.

U-joints are designed with specific tolerances and lubrication needs, and when they become loose, it often means that the wear has progressed to a point where the integrity of the joint is compromised. Continuing to use a worn or damaged U-joint can lead to further mechanical failure, vibrations, and even damage to adjacent components.

Replacing the U-joint ensures that the driveshaft operates correctly and prevents potential issues that could arise from trying to fix it with temporary measures like greasing or tightening, which don't address the root cause of the problem.