The following may help: 2005 BMW X5 TRANSFER CASE ACTUATOR - YouTube

I have used the same carwash since my X was new. They use brushes and 'power wash' the under carriage. There are absolutely no marks on the paint. I use Zaino products.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas