It's according to what route you use. Avoid Teton Pass on 22 between Victor ID and Wilson (Jackson) WY. Grades of 10% in both directions, one of the toughest passes in the Rockies. Many alternatives, let me know where you want to go. You might want to buy The Mountain Directory
, a book that describes each pass and route in the region. Mountain Driving Guide for Truckers, RV and Motorhome Drivers
(By the way the link to book has excerpt of Teton Pass info) Also available: http://www.amazon.com/Mountain-Direc...pd_sim_sbs_b_1
Make sure brakes are good, don't go down faster than you go up, don't 'ride' brakes, firmly apply to drop 10 MPH then let off until needed again. Use engine brake if engine is equipped. Downshift going up for coolant temperature more than speed, don't worry about how slow you're going, it gives more time for sights!