Can long, slow operation kill a tranny? Yes it could, but I doubt it. Before I would say you have a major problem, I would check the simple things first, like the drive belt. When was it last changed, over 3 years ago? If so time to do so. Before buying a new one, remove the deck and crawl underneath. Check the belt tension, look at the condition of the belt, look at the condition of the two idler pulleys and check to see if the idler pulley tension arm has full travel, to keep the belt tight. If you feel everything looks good and the belt is old, replace it. Also replace both pulleys if questionable.
