That happened on my e53 as well and just lived with it. I'd be interested to know what caused it.

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2002 BMW X5 4.6is soon to be LSX swapped. Silver on Imola

2003 BMW X5 3.0i 5 Speed Manual, Sport Pkg, 190,xxx miles and counting. Black/ Black 20" 4.6is Wheels, OEM Stainless Steps, ZHP Shift Knob