We have a RW34SK and have the same sounds. The service tech said it was probably the converter cycling. I can open a panel in the basement and see the converter and it appears that this is what is making the noise. Just a thought.....
Jack & Sheralyn Landon 2012 RW34SK 2010 F250 6.4L Diesel Crew Cab SRW W/Airlift Air Bags & Compressor Kit