I have the same exact problem but my noise starts at 100mph and gets worse. It is extremely loud. The dealer said they wont even look into it because i am supposed to be driving 65mph the speed limit. So i said what about german X5s on the autobahn do those make the same noise because they can do way over 100moh there. I am sure this is not a normal thing for the X5

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Dinan M3

2006 X5 4.4i Sport Current Vehicle
2006 CLS 55 AMG Current Vehicle
2010 FORD F-450 King Ranch Current Vehicle
2012 GL 550 Current Vehicle

1999 M3 Dinan S3 SOLD
2001 M3 Dinan S2 SOLD
2002 M5 SOLD
2004 X5 4.4i sport SOLD
2007 335 XI Lease ended
2009 E92 M3 SOLD