WARNING: This page is about a different car, the 2010 BMW X5, 2009 BMW X5, 2008 BMW X5, and 2007 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
21 OUTPUT SHAFT
Type
Thread
Tightening specification
Measure
1AZ Output shaft to drive flange, rear differential (Torx screw with ribbed teeth )