Necessary preliminary work
WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
Remove O-ring (1) with a suitable tool from front axle differential.
Installation note:
Insert O-ring (1) in groove and coat with front axle differential oil.