4 wheel drive quit on john deere 2210 tractor with a front loader, tractor is about 6 years old with 500 hours?

Does anybody have any ideas? The manager (mechanic) at our local dealer said it was way back in there....at least an auto parts store gives you info...seems like you don't have a choice with j.d. except to take it to them to fix.|||If it is not necessary that you have 4wd for operation it would be cheaper for you to leave it that way. Otherwise you will need someone to crack into the differential case and see why it is not working. It seems strange that a quality unit like J.D. would break at only 500 hours.