The center U joint went out and so I am now replacing all three and the center bearing and rubber mount.

The question is ---- when I pulled the three U joints out, I saw that the U joints had a place where a grease zirt would normally be screwed in. And in the hole was a hex "set screw". No zirt at all. No way to grease the U joint.
If the U joints had been greased, then probably they would still be good. IPD catalog shows a pic of a grease zirt next to their U joints.
Should this zirt be screwed into the U joint and left there to facilitate greasing every 50,000 miles or should the hole just be left closed up with the hex screw?
Should new U joints be greased when put in?

In the OLD days, we used to grease the U joints every 3,000 miles ??? What to do now with these 240 boogers ?

Thanks Bob