It kinda makes a humming sound from the front end
Ball bearings?? There are no ball bearings in the front end of a Ford Explorer, or any other car for that matter. Most cars use tapered roller(drum)bearings. They usually run 10-25$ per side, plus 5-15$ for new seals to put around them. Grease will be about 10$ for a can of good stuff. Do it yourself and save some money on the labor.
