I have towed some fairly heavy trailers with my 2013 Ram 2500, Cummins, etc. I also live in the mountains with some very steep grades. I am also a retired Paramedic that has picked up a few RV'ers that did not know how to drive down a steep grade. You are better off going too slow than to fast, unless you are trying to impress someone (Like Paramedics or Highway Patrol):). As you approach a steep grade (many times they are signed very well) slow to a speed that seems comfortable and sit back and let the Exhaust Brake do what it was built for. If you see that you are slowing too much, just try the next higher gear and be prepared to adapt to the changing terrain. I would rather get to the bottom of a steep grade behind everyone else and make it without the white knuckles. JMHO. JH