What often happens going up some mountain grades, I-70 west of Denver being one of most challenging, is needing to gear down to first gear. But keeping the
RPMs at a comfortable 3500 for example, 35mph or more is usually easy to maintain. Often in fact you catch up to slower heavy trucks, and as mentioned above, it becomes difficult to get around, so with the 4 way flashers on, you just follow them to the top. Going up is not the problem, going down is where care in needed. You need to stay in a lower gear, but even then, the RV's speed will tend to keep increasing, so brakes must be applied firmly and briefly, with keeps them from over heating.