QFT! The engine lets you know exactly when the truck is overloaded and when to shift gears. I am fortunate to have a tachometer on board. I found that my engine (4.0 L V-6) can pull just about anything loaded in any gear when running at 2000 RPM, which seems to be its most comfortable speed. In 4th gear, that delivers 57 mph, and when fully loaded, that's as fast as I want to drive.What it can tell you. Or anyone who will listen. Most don't.
I have to agree, Mark, that many drivers do not listen to their trucks--that is, until they start picking up repair bills.