I had a '10 6.4 King Ranch. Beautiful truck. The bitterest taste of lemon. Ford bought it back after 18 months, 24,000 miles, and $20,000+ of warranty work. It was a turd. Short block replacement, one new turbo, transmission rebuild, and they never did figure out why it had a loss of drive problem while towing doing a 5 to 4 downshift. That was always reassuring trying to get the trans to reengage a gear, any gear, when you've pulled out to pass or started up a hill. The '11 6.7 replacement was as reliable as the 6.4 wasn't. Just traded that on a '16 F150, as I really don't need a big honkin' diesel to tow my 7,500lb 20' car trailer, and while that 6.7 had given me no issues, it was about to go out of powertrain warranty and after the 6.4 experience, a diesel going bad can get terrifyingly expensive to fix just like that. No more stinky trucks for me.