Q: After 20 min. of driving mixed city/highway you can feel resistance and it builds to finely engine stops.

Last time I was driving this truck, after 20.+ Min. I could feel a small resistance when driving on the highway and when I came to a steep hill I was driving maybe 20 Miles/Hour the resistance was building so finely in the middle of the hill it died I had peddle to the floor. While this was happening you could feel the engine shaking. The truck did not have any load. After letting the truck rest for 30 Min. I could continue and drive it home with difficulty. I checked all the normal fluids and that was O.K. Few days later I started it up and it was running like normal and drove it around the block and it acted as normal. I could not smell any thing burnt like brakes or oil. Could it be related to drive train problem?

My car has 150000 miles.
My car has an automatic transmission.