wheel/bearing type noise on ML320 2000

[jeffcfp1]

New to forum, just need some direction on noise most evident 20 to 50 mph(before tire/wind noise drowns out) sounds like metal to metal rear of vehicle, independent of gear transmission is in. My very good neighborhood mechanic doesn't think wheel bearings, thought lip on disc brakes but doesn't see fresh metal there (outside of pad area). Any thoughts or experience? It is not so loud that it would appear to be unsafe to drive, but noticable over tire/road noise at slower speeds. Mechanic says wait till it gets louder. We hate to get "taken" at dealer or tranny shop if drivetrain type issue. Appreciate any feedback. Thanks

jeff b

[davemisto]

bring it to the dealership, very well could be carrier bearing (intermediate bearing), 30 min diag at the dealership will save you from guessing, we fix it right