[Denny347]

At 45mph you start to hear a SLIGHT rumble/hum that sort of sounds like it comes from the front. It gets a bit louder at 55mph and it plateaus there no matter the speed above that. I just changed the thrust arms to correct that problem, I replaced the front wheel bearings about 1.5 years ago, the driver rear bearing was replaced 4 years ago, only the passenger rear is original. I've had the tires replaced and rotated (from side to side since they are staggered) and the noise never varied or moved. My wife doesn't even hear it but I know my car and it did not used to make that noise, it's not normal. No vibrations, just the noise. I jacked the car up today (to rotate my tires Conti DWS) and spun the passenger rear wheel, it sounded normal. Actually I spun them all to double check and they all sound the same. Is it possible that it is the passenger bearing but it's in the early stages of failing so it's not obvious when I spin the wheel by hand? Or maybe the rear differential fluid needs changed (it needs it regardless, it's on my todo list). Ideas?