I know this thread is old as dirt but I am having a similar problem with my JD 4500. Only my issue is worse because it doesn't matter if mine is at idle or full throttle, it will not got into gear. I've tried adjusting the clutch with no luck. I've read that it is possible for the clutch to rust to the flywheel? It had only been a week or so since I'd ran the tractor. Anywho, I dropped it off at the mechanic this mornin but I happened upon this old thread and thought I'd see if there was ever a resolution? Thanks for any help