I race this truck up in the mountains and am constantly shifting up or down manually to take advantage of the higher rpms . I havent had a problem yet but then again even if i do thats just a real good time to upgrade the tranny!!!!

 

The torque converter is slipping, and that generates heat. The less heat the better. Of course it won't damage the geartrain if your not moving. Same with a manual tranny, but its hard on the throwout bearing. I have learned these techniques from my father who has been driving this way longer than most of us have been alive, he is stubborn and even downshifted a mini bus that he used to drive, and a caddy fleetwood stretch limo, he is an enthusiest, and thats just the way he drives, with anything. Many a tranny have survived many a miles with him, people always question it, but there is proof, with hundreds of thousands of miles on many different generations of autos. Even the modern "delecate" electronically controlled trannys from torqueless front drivers. Not only the Turbo Hydros from the 70s.