Nothing is wrong with them unless they are abused.
My first 99 F350 went 115,000 towing 10,000 - 17,000 lbs DAILY. It failed because of an abusive employee...
My 2002 F350 Dually has 160,000 on it now with the original tranny. Working harder and pulling heavier then the 99 did/does. Frequent trailer loads up to 30,000 lbs. Nothing g wrong with it at all.
See above ^^^ Nick