Analysis of Leakage
WARNING: This page is about a different car, the 2007 Lincoln MKX and 2007 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.
Clean up the leaking area enough to identify the exact source.
A plugged rear drive axle housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.
Verify the axle lubricant level is at least 3-5 mm (1/8-3/16 in) below the bottom of the fill hole.