One problem related to automatic transmission floor shift has been reported for the 2005 Mercury Mountaineer. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Mercury Mountaineer based on all problems reported for the 2005 Mountaineer.
Transmission lever binds when attempting to shift into park, slipping into reverse instead. Problem has occurred sporadically from 2007 to date. Usually the miss-shift is noticed because it just doesn't feel right, but not always. It can be most dangerous if you don't turn off the engine immediately (after attempting to shift into park) and take your foot off the brake. That has happened to me about 5 times over 5 years. It happened twice at a gas station, once at a car wash, once in a shopping center, and once in front of my house as a child walked behind the car. In each case the car only moved 1 or 2 feet before I realized it, and was able to step on the brake. These days I don't need to worry about it as much because (at 52,000 miles) the transmission takes 5 - 10 seconds to engage the reverse gear and then it bangs into gear, loudly alerting me that it didn't go into park. . The transmission is defective, and Ford knows it.