[Jacques Reed]

Just had a look at my 4-7/8" steering ends on my F-15A. I could not remember seeing plugs in the lower part of the ball sockets. A quick look confirmed that there are no plugs in them.
I then had a look at a couple of ball socket spares and they were drilled and tapped for plugs so at some time the plugs were added or removed during production. Which came first though?

I also noted that there is an identical plug that fits my tapped ball socket in the end of the CV joints. Could that be a lubrication point for the CV joint as it goes all the way through to the balls and cage in the CV? The pilot pin which fits in the end of that CV joint hole has three grooves in it which may be to let grease pass under pressure into the innards of the CV joint. There is nothing in the Maintenance Manual regarding this but perhaps it was just common practice.

As suggested here, filling the ball with grease causes more problems than it solves unless it is accurately directed to where it is required which is inside the CV joint.

Perhaps the plug in the ball housing is more for draining water after front axle immersion than for lubrication?

Cheers,