Wet Diff in Cold
Some 2011-2013 Ford Flex vehicles equipped with a 3.5L GTDI engine may exhibit an occasional fluid leak coming from the rear differential vent cap in temperatures below 32 degrees Fahrenheit.
Inspect the rear drive unit for oil leaking from the vent cap located on the rear cover. A slight residue is normal. If a wet fluid leak is found, replace the vent, P/N DB5Z-4022-A and clean off any remaining residue.