There are 1 owner-reported powertrain & transmission complaints for the 2010 Mercury Mountaineerin NHTSA's database. These are unverified consumer reports and may not reflect confirmed defects.
REAR DIFFERENTIAL IS FILLING WITH WATER PASS THE FILL PLUG. THIS IS A GARAGE KEPT CAR AND NEVER OFF ROAD NOR DIRVEN IN DEEP WATER. FIRST TIME DISCOVERED AT 22000 MILES AND THE DEALER REPLACE THE PINION SEAL AND OIL, BUT COULD NOT FIND THE CAUSE. DIFFERENTIAL NOW MAKING NOISE AND AGAIN FULL OF WATER PAST THE FILL PLUG. SEARCHED ONLINE AND FOUND SEVERAL PEOPLE WITH THE SAME PROBLEM WITH FORD PRODUCTS. DEALER CANNOT FIND OR NOT WILLING TO FIND THE CAUSE. CALLED FORD AND THEY OFFER LITTLE TO NO SUPPORT. GUESS THEY ARE WAITING FOR THE DIFFERENTIALS TO LOCK UP AT HIGHWAY SPEED AND KILL A DOZEN OF SO PEOPLE.
Complaints are unverified consumer reports submitted to NHTSA. A high complaint count may reflect vehicle popularity, not defect severity. Data sourced from NHTSA public records.
Data synced from NHTSA on Apr 26, 2026