Just to clarify.
I totally cleaned the gearbox internals when I rebuilt the bike and did not pack it with grease. After assembly I filled it with a tube of the 00 grease. I did not know if there was a specific method for removing this other than getting the bike good and hot then draining. I was wondering what the Owner's Manual recommended.
Cleaning with ATF sounds like a good idea, but with the old felt seals in my bike, I think most of it would come out before I reached the end of my driveway!
Andy