Is this something new. Cummins engines whine or whistle as a normal sound. The pitch changes with RPM but it can be clearly heard if you have your window open and are driving slowly through a campground as an example. You can also tell the big rigs that have Cummins engines on the road by the whistle they make - it comes from the turbo charger. Sorry if this is something you already know. We had an 07 Endeavor 400ISL and it whistled and now we have a Camelot with a 425ISL - same sound.
2016 Winnebago Cambria 30J