I couldn't tell you exactly what it is, but I complained because the transmission seems to get lost and not know when to shift. It hangs going up hills and somethings flutters when I want a medium downshift. It reminded me of the tranny on my old Ford Taurus SHO right before it failed. My dealer spent time with BMW tech doing all kinds of tests and the shift module was the only thing acting up.

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PhoenixM3
2008 M3 Sedan - Interlagos Blue [On Order]
2008 X3 3.0is - Black Sapphire, Sport Activity, Premium, etc.
2007 X5 4.8i - Deep Green, Sport, Premium, Technology, Comfort, etc.
2005 X3 2.5 - White, Bare bones, Auto (My business delivery vehicle)
2001 M3 Convertible - Phoenix Yellow, 6-Speed