That's a very good question, Otto. I can see where adding the Mineral oil could loosen up the grease that's in there but I'm also thinking about it creating a leak at the seal on the shaft. I "overhauled" my gear box by installing new bushings and a new seal and then filled with cornhead grease. My initial issue was play in the output shaft ( a lot ! ). If you end up going with the oil added, let us know how it turned out if you would.
