Various problems with the 5-speed automatic transmission were common. These problems can be more common on the 2002 models with build dates before March, 2002. There are many service bulletins describing the diagnoses and repairs, which include fluid leak repairs, transmission software updates, or internal failures requiring a costly repair.Google+
Car Problem Reports
Mercury Mountaineer Problems With 5-speed Automatic Transmission are Common
Mercury Mountaineer Problem
Drive Trains Affected: 2WD, 4WD
Average Mileage: 118,940 mi (70,000 mi - 164,000 mi)
Visitor, 2002 Mercury Mountaineer, 4WD, 70,000 mi
Transmission started down-shifting at speed. New transmission and bore and servo work : $3400
Visitor, 2008 Mercury Mountaineer, 4WD, 87,000 mi
Transmission failed requiring total rebuild.
Visitor, 2002 Mercury Mountaineer, 4WD, 110,000 mi
would not change gears needed new transmission
Visitor, 2002 Mercury Mountaineer, 4WD, 120,000 mi
Per Transmission shop needs new transfer case & possibly may need entire transmission rebuilt. GREAT!
Visitor, 2002 Mercury Mountaineer, 2WD, 120,000 mi
Had to replace servo bores in tranny along with major overhaul. $2600!
Visitor, 2002 Mercury Mountaineer, 4WD, 102,900 mi
check transmissin message. Incorrect gear ratio 5th gear reliable tranny shop $2,100 mercury $3600. Light only came on once.might look for new car
OD off flahes in msg center, and check engine indicator comes on. Waldorf Ford recommends trans replacement @ $3700.00