There is a rev limiter but you are not hitting it. There is no governor either. I believe what you are finding is how expansive Colorado grades are. Because of size, you think the grades are less steep than they really are.
If you are topping grades at 4k RPM and going 40 MPH you are in second gear. Try lifting the throttle a little and pulling in third gear. You won't go any faster but the engine will be much happier and make a lot less noise.
Just to give an idea, those grades in CO. are steeper than climbing out of the gorge south of Saint George, a place I know you know. How does your coach handle that one?
2015 Jayco Precept 35UN
Towing JEEP TJ with Roadmaster plates and bar w/Blue Ox Patriot brake
an Aluma low bed trailer with HD Road King and/or Polaris RZR onboard