jettruck

My 2010 R-350 4matic has a front-end drivetrain howl I can't get rid of. It's always there unless I turn right or apply the brakes. Told it was the right side bearing and took it apart, everything looked ok, including the half-shaft. It didn't go away. I took the left side apart and replaced the upright/hub assembly, and installed a new half-shaft, thinking that side had to be it. Howl is still there. Changed the differential oil also, and it looked OK. Have any had this experience or have any ideas? Thanks