Sorry, VERY old thread...
Looks like I have a leak at the seam on my front diff now.
Found it while having the oil cooler/alternator bracket leak fixed.

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2008 4.8i X5 (2/25/08) 105k:
Titanium Silver/Black; All -HUD; Aero Kit; 22" VS-130 w/Pirellis;
///M Shifter & Fr Brakes; Gauge Rings; Console Pads; Custom Wheel & Mats; Roof Rails
Carbon Fiber: Int Trim, Nav Surround, Grill, Cluster Trim, Shifter & Eyelids
1.2" H&R; LUX AEs; LCI Tails; Rear Fogs; NBT EVO; ESS Tune; Meisterchaft GTC Exhaust