Originally Posted by tallguy
I'd say not only rpm but torque as well, makes a hell of a difference if you're going downhill without any load on engine or uphill when trying to manually shift, no?
In my experience, it makes no difference going uphill or down, towing or not towing. RPMs are RPMs and it doesn't care about engine load. I can shift up to the same RPMs regardless.
Having said that, if I shift up to a gear where it's not able to maintain speed on an uphill, it will eventually drop back down on it's own if the RPMs start dropping from losing speed. I can have the accelerator to the floor trying to maintain speed, but it won't downshift until the RPMs start dropping.
The transmission has no idea whether you're on a hill or not. It only knows what RPM you're at.