I've got a L3600 GST 1,930hrs. Gears 1 -4 are as stout as ever but gears 5-8 fills like the clutch is slipping. It will move in the high gears but only on flat ground. Feels like the clutch, but I would think it would slip some in 4th gear if the clutch was gone. 5 gear has made a slight noise in the past but just for a second when getting the tractor moving. I have not noticed any noise or problems in gears 6-8. Maintenance is up to date. Anyone have any ideals?