If you feel that you are braking too much going down hill, then manually shift down one gear and see how that goes! If that works then your where you want to be on a downgrade. If not and your on a extremely steep downgrade (like Chinook Pass in Washington State, West Side of pass) drop two gears manually. On I-90 highway speeds with the Jake On and slight braking should do the trick for you. I've drove diesels (semi's) my whole adult life (44-1/4 years) just so you know who is giving you this advice. And on your dehumidifier I take mine everywhere I travel especially in the Northern Tier States where your going. Good Luck in your travels.