7mm Transmission too loose (but not the press fitting)

[bwg]

I wonder if someone has a fix for a 7mm transmission (although I'd bet an 8mm would do the same thing) that has become too loose. It was actually my doing. I put a drop of 3-in-1 oil in the trans because it turned very stiffly. Now it is exactly the opposite. It is so loose now that the pen is uncomfortable to use.
Maybe I should have just lubed the transmission with pure oil instead of 3 in 1.
Any ideas?

 

[Jolly Red]

Take out the transmission and replace it. Spares are available online, and may be useful later, also.