Dr. Hamman is obviously offline, maybe I can help. I only have one question because this had just happened to me after inheriting my brothers 2005 F350 with the 6.0 diesel. While I was driving it back to my house, towing my 1990 Chevy C2500 on the back with an UHaul car trailer, I encountered a mountain here in south western Pennsylvania. I saw the sign which said downshift into a lower gear and after trying just that for a few seconds, decided no, that's not for me. Big mistake. I had just stopped for lunch and the tow button had reset to off, which I really didn't know what it was for anyhow. The hitch was 2" into a 2 1/2" receiver, so the truck and trailer I was towing began swaying back and forth at around 50 mph, so I put the cruise control on, set at 45 mph. Mistake number 3, including the tow button as number 2. So, I started up the mountain, with the transmission in drive, not a lower gear, the tow button off and the cruise control on. The computer kept flooring the throttle trying to maintain 45 mph, which it couldn't, the tranmission was in drive and the tow button was off. I overheated the coolant within a mile. Let it cool down a little, added 2 gallons, and then overheated again within another mile. I spent 4 hours on that one side of the mountain overheating and trying to find water.
Long story short, I thought something was wrong with the cooling system. It runs fine now the last month or so problems overheating at all. I figured it must have been my fault and nothing wrong with the cooling system. After having the Ford 350 towed home, I read about it. It appears, the tow button locks up the torque converter and prevents the transmission from constantly up and down shifting, which helps prevent overheating or either the transmission and/or the engine coolant (radiator). The transmission should have been dropped to a lower gear and allow the transmission to work smarter and not harder and 3rd, turn off the cruise control, which probably would have been off anyhow, if I would have just downshifted.
Lesson learned, when towing up a mountain, downshift, turn off the cruise control and use the tow button, if you have it.
So, my question is to you. Was the engine getting hot and is that why it was loosing power and going into limp mode? If so, it may be nothing wrong with the vehicle at all except like I experienced.