I have almost new 350s with an 11-speed XD driver. When coasting, the freehub sound sort of pulses. It's hard to explain but the buzz is not consistently the same tone. It has a rhythmic pulse where it gets louder. Anyone know what I mean?
There is too much grease in the freehub body were the star ratchets are. Watch the video this will give you an Idea for what to look for. https://www.youtube.com/watch?v=g8ZQJS0IQM0
I have had other hubs make a similar noise after regreasing but I have cleaned pretty much all the grease out with only a light film of oil and it still does it. Really weird but I have over 2000 trouble free miles on it so I can't complain.