If the transmission oil leaks out of left side half shaft area, it may be from a worn axle shaft seal. The seal can be damaged by a poor surface finish on the axle shaft. The axle shaft and seal should be replaced to correct the problem.Google+
Car Problem Reports
Mercury Milan Transmission Oil Leaks from Left Side Half Shaft Area
Mercury Milan Problem
Drive Train Affected: Automatic Transmission
Average Mileage: 55,100 mi (25,000 mi - 95,000 mi)
Visitor, 2010 Mercury Milan, Automatic Transmission, 41,000 mi
Leaking in the half shaft. The dealer replaced it under warranty. After approx 6,000 miles it started leaking again. The dealer replaced under Ford TSB 11-30-11.