Yep, driving at a higher RPM would have forced more air through the transmission cooler and we would not have blown a seal on the tranny. Wish we had known THAT before we went up Priest's grade.
While we were cooling down and letting that seal reset... I managed to get on the internet and RV.NET guys gave some great info and advice. That was to ADD a cooling unit in series (instead of just replacing the one we had with a larger one.) Put them side by side. GREAT advice for us. That's what we had done the next morning.