I just fixed a noise on our coach that was rhythmic and pretty deep tone that turned out to be the stainless steel wheel cover. I removed it and the noise went away so I spaced the simulator out with a couple of 1" dia. washers. May not be your issue, but it fooled me...not that hard.
2004 37B Adventurer, 8.1 WH, Ultrapower, DIY CAI, Henderson Track Bar, Tru Center, Koni FSD's, Roadmaster Even Brake, Scan Guage II, 180 Thermostat,