Grillo G85 D Slips out of second gear

[mtnpete]

I bought this tractor about 10 years and use it as sickle bar mower exclusively. A couple of years ago it began to pop out of second gear. Joel at Earth Tools send me shims, including a custom one he made, and a new spring for the detent but it still pops out occasionally, and the whole shifting system feels mushy and getting mushier. I've been sticking to first gear going up hill (don't want to break my legs--steep hill) but whereas first gear used to feel "locked in," it feels less and less that way. The thing is shimmed to the max as far as what Joel says, and he has always been right on the money so I'm wondering whether there is an internal problem. Hard to tell from the parts schematic. I thought maybe the clutch adjustment might have something to do with it (not enough freeplay) but unfortunately not the case. Anyone out there have a similar situation? I still have four or five more mowings this year.