oops. This "chuck" guy....he should pull one end of the driveshaft off (preferrably the end with the slip joint...but the other end will work too). Then if he were to compress the slip joint by hand, it would force the excess grease out of the weep hole in the end of the slip joint. The joint will be a bit stiff at first, then ease up, then get tight again once "chuck" gets to all the grease. He should keep pressure on the joint until it is fully compressed. Then he should wipe up the grease that is all over the place, dispose of it in accordance with federal, state, and local ordinances, re-install the driveshaft, and not overgrease it again.
:ylsmoke: