Hi guys, I picked up a 2013 328i 6 speed sedan about 8 months ago and love the car. However I noticed that the drivetrain is making a whining sound when coasting down from freeway speeds. The sound disappears around 45 mph and below or whenever my foot is on the throttle. It'll whine when coasting regardless if it is in gear or neutral. It sounds like a fairly hi-pitched "wooooo"

I can only hear it with the windows UP and I think its coming from the rear of the car, perhaps differential?

The car currently only has about 36k miles on it too. Everything in the car feels fine too, no odd clunking noises, goings in/out of gear effortlessly, and overall feels very tight with the exception of the sound I described.