There's two ways I do this....If I'm pulling a load, or have a truck full of people/gear, and I'm pulling an incline/steep grade, I will manually downshift it to 3rd to make CERTAIN that the tranny does not try to shift into 4th/overdrive too soon...the lessor amount of shifts that tranny is doing while climbing a mountain, the better off you are in keeping it cool, and keeping it locked in 3rd assures that you won't overwork tranny or the engine. There have been times I've had to even downshift into 2nd, but those times are VERY few and far between, and generally only if I'm on a VERY steep back road, in which top speed is 15-20mph, maybe.
2nd option....if the truck is empty or only half loaded with just people and not much gear, I will leave the tranny in *D* and push ON the power mode BEFORE even beginning the climb up the grade, this is the *sport* option gearing, if you will, for this truck and tells the tranny which gear is best for the road its experiencing. Many of times, with 2-3,000 ft inclines over the coarse of a few miles, the powermode is enough to keep the tranny/engine from lugging.
However, if the truck falls below 45mph in powermode, suddenly the tranny will do a harsh downshift into 2nd and send the rpm's to over 4,500...I don't like this, and prefer not to let it happen, but sometimes it does. At those times, I immediately shut OFF the powermode and downshift it to 3rd, where I will allow her to coast up the hill at 40mph at a decent 3-4k rpm's...I don't like to overwork the engine or tranny.
I do live in the Colorado high-country, thus I downshift and use my power mode a lot, specially while towing. These habits can prove to work wonders for keeping these trannies cool; the worst thing you can do to this tranny is overheat/overwork it.
Your winter mode feature is probably something that you won't use too often if yours is a 4x4, but could be something you try BEFORE putting it in 4-wheel drive. Pushing the winter mode ON simply starts the truck off in 3rd gear from a dead stop; i..e when your stuck on slippery ice, stuck in sand, mud, etc. it automatically shuts off once you reach 15mph.
This is a GREAT feature that I have used a few times with owning a 4x2 Rodeo in snow country.