If you have a FORD ESP it’s unlikely they wouldn’t cover it but... this part above confuses me.
You have to drive it off the mountain, got that. you drove to the closed stealership and they told you ‘begone, peasant!’ ? presumably they were too busy. On the way to 2nd stealership the diff came apart. - Correct?
this part sometimes causes manufacturers to lose their common sense with the “well, Mister soandso, you knew the truck had a problem, continued to drive it and made the damage worse. Neglect! No warranty for you!”
During my decades ago lemon law suit; I think it may have been the incident the actually started it; I had been in for a transmission repair, down 3 weeks, got it back and thought I saw trailing smoke when I got it back. I couldn’t recreate it. I though I saw it again and had someone follow me - they confirmed it. I call the stealership service department, they tell me ‘drive it in, we’ll take a look’. I’m like “drive it, you don’t want me to tow it?” No, says they, it will be fine.
From that point on, it shifted funny; I say wrongly, they disagreed, but it was different from other vehicles like it and not for the better.
I was questioned on that event pre-trial, they tried to make it a thing, but the service mangler, to his credit did not deny my description of the events.
It sound like your truck was drivable until the first stealership shooed you away, that’s a tough thing for Ford to say isn’t their “fault”.