We have a 2003 Class C with the V-10 and it doesn't even have a tach. I think if you are at all familiar with engines, pulling loads, running high RPM's etc. the engine will be really noisey and sound like it's screaming well before it would reach a danger point. Especially true with an RV where super high RPM shouldn't be necessary if you are in the right gear. It isn't drag racing where you want red line revs. When I towed with a truck, Chevy v-8, 4500 sounded high but it isn't.