A. Good question and an area that is most often neglected or done incorrectly. Many truck 5th wheels are re-lubricated by simply taking the grease dispensing unit and dispensing a ribbon of grease around the 5th wheel plate and often neglecting the 5th wheel jaws which engages the trailer pinion entirely.
To properly lubricate the 5th wheel, one should trowel the grease with an even film not too thick, 2/3 up the 5th wheel beginning at the bottom and proceeding 2/3 of the way up with more grease at the bottom allowing for trailer displacement of the grease upon engaging the trailer. Grease should also be applied to the jaws to reduce wear on both the jaws and the trailer pinion. Using heavy duty grease designed for higher loads encountered in heavy duty trucking and applying these practices has proven to add 100,000 of miles to 5th wheels before rebuild.