If it's above 40 mph, and unnoticeable below, probably wheel bearings. Tell tale sign is taking turns above 40, it will quiet down depending on what side the bad bearing is, and which way you are turning.

I would replace in pairs if it is wheel bearings, as good practice.

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards