 January 2018 update:  I followed through on opening a Lemon Law Case with the Better Business Bureau (BBB Auto Line) and followed all the required procedures to the "T" all the way to and through the arbitration process.  Since the case was heard remotely, i.e., the car was out of state at the time of the hearing, the arbitrator could not personally drive the car to evaluate the noise complaint.  The BBB Auto Line Representative dispatched an independent expert to my out of state location who drove the car and submitted his report to the arbitrator.  The independent expert, who had over 25 years of mechanical experience, heard the whining noise as described in my complaint immediately upon decelerating and even identified the probable cause and location yet the manufacturers traveling engineer and dealers service team could not!  Long story short:  I won the case and Hyundai had to refund the full purchase price and take the car back as a lemon.  It was hard for me to believe Hyundai would rather put a long time loyal customer through this laborious and time consuming process and ultimately have to refund the full purchase price of the vehicle instead of simply replacing the transmission.  Perhaps they thought I would just give up and not follow through to conclusion.  They picked the wrong guy for that!  Here's the clincher:  After an extensive test drive of a 2018 Genesis G80, I bought it.  Crazy?  Time will tell but this one has absolutely NO whining noise at any speed!July 2017 update:  The noise persists!  After repeated contact with the dealer and Hyundai Customer Care I was finally able to convince them to have their traveling engineer drive the car and assess the noise.  After he drove it, he authorized replacement of the differential!  Great I thought...until I drove the car after the repair because the noise was still there.  I decided to open a case with the Better Business Bureau Auto Line.  One of the procedures using the BBB is that I have to send a Motor Vehicle Defect Notification Form by accountable mail direct to Hyundai in California.  They, according to the instructions I received, have to contact me within 10 days after receipt of my form to schedule an appointment for a final assessment.  They didn't contact me.  I notified BBB Auto Line of that and they reopened the case.  To make a long story short(er), I and the car are now in Virginia for the Summer, the noise persists to such a point that I want to park it and not drive it.  Hyundai is not being very responsive and I'm losing hope that this whole process will come to an end before the warranty expires.  Is this a lesson learned?  Definitely for me!One of the nicest looking and comfortable cars I've ever owned.  However, I have one major concern.  When I test drove this car I admit I was distracted by the comfortable ride, all the gadgets and technology and wasn't specifically listening for strange noises.  Who would expect to hear any noise while driving the flagship model?  My bad!  After a couple days of driving the car with the radio on, I took it for a drive one day and for some reason, I didn't turn the radio on.  During this trip I heard this strange "whining" sound that appeared to be coming from behind the drivers seat.   At the time I first heard it I was decelerating from about 45 MPH.  The noise persisted until I reached 35 MPH then is stopped.  Thinking I was hearing things, I drove on  a smoother road up to about 45 MPH then decelerated.  The noise was immediately noticeable again and continued to 35 MPH.  OK I thought, this was a very expensive car...the most expensive car I've ever owned and I have a "whining" noise?  Seriously?  I took it back to the Hyundai dealer who test drove the car and came to the conclusion that the noise was "road noise" and was "normal."  This diagnosis was based on the service manager driving another Genesis (same year, make and model) and hearing the same noise in that car as well.  You cannot hear the noise if you're in the passenger seat.  I thought, wouldn't you hear "road noise" on either side of the car?  Not being satisfied with the dealers response I contacted Hyundai Genesis Customer Care.  After several phone calls their final decision was the noise was "normal" based upon their reaching out to the dealer who relayed their same car test drive theory.  Of course Hyundai Customer Care was not about to go against the dealers diagnosis.  While I am impressed with the Genesis, I am disappointed that I paid for what I thought was going to be the best car of my life: quiet, comfortable and full featured and got a car with a very distracting "whining" noise.  Over the years, I've owned no less than five Hyundai models (XG-350, Santa Fe, Sonata, Tucson, and now the Genesis.  I have never heard a similar noise from any of the previous Hyundai models...until I bought their flagship model.   Unfortunately this will be my last Hyundai!