Actually, I remember reading that tranny fluids have a linear relationship between operating temp and miles, the higher the operating temp of the fluid the shorter the useful life of the fluid. Just made up numbers but say, running temp of 200 would be good for 100k, running at 300 would be good for a few hundred miles, or maybe it was temp and time, not temp and miles. So, a scenario where you are dragging a 15k lb. trailer up the mountains regularly, it could be that the fluid is "smoked" as you say, and would just need to be changed, assuming no damage to the tranny internals. And, all that is assuming you are monitoring the tranny temp and miles/time. My $.02.
In the back of my mind I have wondered if some of our transmissions are perhaps under-filled from the factory, it seems that some of the engines may be arriving low on oil, just from reading on here and my experience with my truck. My transmission shifts funky sometimes (rpm's flare up shifting into 8th), I guess it wouldn't hurt to check the fluid level, if possible. Already had the reflash done.
