We have a 2018 3790RD, we had the same issues. Run the water for both hot and cold on your lower freeze lines to bleed air and then run all other lines to do the same. As stated it will never be noise free when running the pump. I also had to put washers on the pump legs due to over tightening from the factory install. You can access the pump by removing the basement wall next to the city water inlet.
