Concern or coincidence?

I wonder if making the truck shift while the tires are spinning like that could have been part of the cause. Hopefully someone a little more knowledgeable could chime in on this.

 

I doubt it, these autos shift pretty smoothly with no grinding. Possibly a little more strain on the clutches/brakes but I doubt much, since it probably is no different than shifting under normal load for them. They were just towards the end of their life due to overheating and it was their time to go. Most likely the tranny fluid was bad from being overheated a time or two during all that towing and it was slowly wearing out the wet clutches and they finally gave out. A fluid change probably could have helped the tranny out a lot, but since the previous owner is likely the one that ruined the tranny and warranty covered it for OP, this was best for him.

 

From what I recall I didn't hit high enough wheel speed for it to shift I could be wrong, I don't think that would cause damage tho. I was gonna get my tranny serviced at 60k but now that I'm getting a new one guess I don't need too. Either way I have decided not to worry about it and still use my locker mod lets all just hope this crap don't happen again

 

Makes sense. I've always put my truck in 1 if I'm going to break traction because I was nervous about making it shift under those conditions.

OP is a lucky man.