Take a good look at the round thing just below the "R" in your first photo, clean it and see if there is a wick in the center----------I have seen things like this where you apply a drop or two of oil to them. Also, if there is a ball, that you can push down, it is for use with an oil can with a skinny applicator tip, or grease gun with needle tip.
Not sure if this is actually what you have there, but worth checking it out.
I don't have that exact model but the head looks the same. Mine came apart and I was able to grease the internal gears by unscrewing the nut that retains the portion that the threaded bit screws into. Before I did that the head of the drill would get so hot that I couldn't hold onto it - after I greased it it ran cool. Big difference!
