My 2014 Model S 60 (with 61K miles on it) has a definite motor whine but only on acceleration. It sounds sort of like a jet engine winding up during any acceleration but instantly goes away when I let off the accelerator. It is most noticeable at low speeds, though it seems to go away above 35-40 mph when wind and road noise drowns out the whine. We had the 5-yr/60K service done on it last December but I suspect they never took the car out for a road test during the servicing. Besides our Model S 60, I have driven a 2016 Model S 75 loaner car and my son's 2018 Model 3, neither of which have any noticeable motor whine at all. Is this motor whine anything I need to be concerned about? Is it specific to the earlier Model S 60 motors? I'd appreciate any input you might have. Thanks.