This question is somewhat after the fact, but I am still curious. What is the best way to handle hills, particularly downhill, when towing? When I was driving through the mountains in Northern California and Southern Oregon on Interstate 5, I put the truck in second on the downhill sides. It did not make the RPMs go haywire and I was able to keep my vehicle from going too fast without destroying my brakes. Was this correct? What role, if any, does the Overdrive play in all of this?

 

I drove the northern CA and Oregon I-5 corridor this summer pulling a TT. I drove with the OD off and did real well going down hill and was good to go up hill. I think that with the OD on you would lose any engine braking going down hill.

 

Keeping your truck out of OD while towing helps maximize your HP. If you check your owner's manual you'll see that the max HP is produced at higher engine RPM; by keeping the transmission in 3rd instead of 4th the Revs stay closer to the optimal portion of the power band. OD exists because you don't need all of your HP to move the unloaded truck at highway speeds, so it switches to an even higher gear that allows the engine to operate at lower RPM, which gives you higher MPG and lower engine stress.

Manually selecting a lower gear on steep downgrades was exactly the right thing to do. The "engine braking" you get by selecting lower gears puts considerable drag on the vehicle and the higher RPM won't hurt the engine provided it isn't excessive.

Keeping your speed down and your gears low are very important when towing, especially in steep grade conditions. I white knuckled a ride down into Cody WY after overusing brakes on what I thought was the steep grade-until I hit the REALLY steep grade. Good thing there was a big parking lot at the bottom.