RAM 3500 AISIN tranny shifting

[vipermanden]

Dumb question here. I got my new SOB 5th wheel, and it is 4,000 pounds heavier than my Montana 3820FK was, and coming up to my house in Tahoe, is a 11% grade for about 3 miles going over the Brockway summit, which is 7,200 feet. Usually in the Monty, I could keep 50 mph over the summit, but now this first time I went over the summit, it kept slowing down to 40 mph, and did not down shift for the longest time, when it was too late. I ended up going 35 mph over the summit. Do any of you take it out of Tow Haul mode when you know you will be going over a mountain pass, and you want the tranny to be more responsive? Also, what about that + - button on the shift column? I read about using that, and it is confusing? It says tap the minus button once to activate it, and tap it again to control the top gear you want the tranny to go in. To turn it off, it says to hold in the + button, until the "D" appears in your dash? Any of you use this to manually downshift??? Thanks