My Dad has a 2000 F150 he bought with 10,000 miles on it. It has the 4.6 and he's used it as a work truck and towing a big boat a lot too. It has 350,000 miles on it and running good still. He changed the transmission at 250,000 mostly because he tows a boat that's a bit too heavy for the truck and he pretty much never comes to a complete stop before changing from reverse to drive. He just changed the fluids/oil religously and there ya go.