sounds like leaky air springs.

No.1 in the following for rear
RealOEM.com * BMW E53 X5 4.8is LEVELL.DEVICE, AIR SPRING AND CTRL UNIT

or No.1 in the following for front.
RealOEM.com * BMW E53 X5 4.8is Levelling device/air spring strut/sensor

__________________
StumpyPete



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