384,000 miles on 7.3 turbo diesel. With regular maintenance these things are extremely dependable. No major problems with engine or tranny. I did have to rebuild the rear-end at 300,000. I have hauled some pretty heavy loads. Always averages 20+ mpg hwy.
The big D (diesel). This thing will haul or tow anything.
Glow plug relay dies annually. More durable alternator.