Have a look at the vent cap on the axle. These have a nasty habit of leaking and the oil works it's way down around the differential and looks like a pinion leak. Mine looked the same so I fitted a JLT expansion tank, cleaned off the oil and it has remained dry since.
2013 GT Premium Brembo
MGW, Blow Fish, AM Hood Struts
Tinted, Borla Touring AB, ProCal Tune
Full Shelby/Kicker Audio Upgrade