I had this same problem with my Charger Hellcat and was told it was due to "straight tooth gearing" but I have some whine when I let off the throttle at lower speeds (typically at or lower than 40mph). They initially replaced the rear diff unit on the Hellcat and the new one had the same noise. I then had them add some some additive to my Charger Hellcat when I had it and seemed to help slightly. Any suggestions on this? Anyone else deal with this? I don't experience any binding or issues but just more curious? This could all be design related.