Unless your RV travels are limited to the Midwest or coastal areas or the East, sooner or later you are going to face driving mountain grades. On the way, upgrades can cause overheating and drive train wear and tear, while the downhill run poses the risks of burning brakes and losing control. By using your transmission effectively, you can make the drive on both sides of the mountain easier and safer.
Mountain grades lead to spectacular places. Although your actions will differ depending on whether you have a manual or automatic transmission, the approach is the same. On the ascent, you want to keep your engine and drive train operating in the most effective range of its power curve. Heading down you want to use the drive train to help maintain control while preserving your brakes.
Optimal engine speed and gear selection when climbing any particular grade will depend on your engine size and type – gasoline or diesel, your transmission and the weight of your RV. Regardless, on grades keep your RPMs in the power range by downshifting as necessary. Start by building up some speed and dropping out of overdrive as you approach the slope, and if you are going to be in the mountains for a while, stay out of overdrive. With an automatic transmission you may not have to do anything else, just let the tranny take over.
With a manual, downshift whenever your tachometer indicates that you are in the lower part of your power range. Watch the engine temperature, slow down and gear down to reduce heat buildup. Be prepared to pull off if possible to prevent overheating and, if you do, leave the engine running for a few minutes at fast idle to keep your coolant circulating. If you have a temperature gauge on your transmission, watch it also; you don’t want to ruin your fluid by letting it overheat for any length of time. Again, pull off and idle if necessary.
Heading down the other side, it’s all about control. If there are curves, holding down your speed is essential for safety. The longer and steeper the grade, the more you will want to use your drive train to help control your speed. Using brakes alone can cause them to overheat and lose their effectiveness when you most need them. On grades of 5% or less, running with overdrive disengaged may be sufficient, but steeper hills will likely require lower gears.
A common practice is to use the same gear going down as you used on the way up. This may vary with your weight and vehicle. You’ll learn as you gain experience, but start slow and in control. With an automatic transmission, you will need to drop it into lower gears yourself. Keep an eye on your engine speed and use your brakes to avoid red-lining or going too fast. But do not ride your brakes; apply them in short, hard bursts to reduce your speed.
These are general ideas. Be sure to read your owner’s manual for any specific driving instructions that the manufacturer recommends.