Just came across this thread -- Did you end up getting the transmission replaced or fixed?

I'm also getting a "hoot" / whine noise on my x5 when accelerating and downshifting. I recorded the noise -- can you have a listen and see if this sounds like the same transmission noise that you have?
X5_Shift_Noise.mp3

FYI - Here is the thread that I started: Clicky

Thanks