Packing a universal joint is easy if you follow this procedure. When the joint is disassembled, wipe out as much of the dirty grease in the cap and cross as you can reach with a clean rag. Then fill the cup with clean grease and force it back on the cross shaft, twisting it back and forth with the palm of your hand. The dirty grease will be forced out and can be wiped away. Repeat until the grease comes out clean. Now you can fill the reservoir and reassemble the universal joint.