Towing, Grades, Hills, PRND321
When going up hill you want to lock into the highest gear you can to maintain a safe and prudent speed without having the transmission constantly up shifting and downshifting.
As a rule I will pull up hills up to 4500 rpm, but if the hill is very long and very steep I will hold the lower gear and take my foot out of the accelerator to about 4000 rpm.
Going down pick a speed and gear where you are not constantly on the brake pedal. On a long and steep grade you want to use the brakes no more than about 5% of any downgrade. Less than 5% is even better.
You can learn your vehicle by stopping at the bottom of a grade, if you can smell your brakes downwind, you used them too much. Adjust accordingly.
The fact that I am opinionated does not presuppose that I am wrong......