Some 2002-2010 Mercury Mountaineer vehicles (as well as Explorer and Explorer Trac) equipped with the 4.0L engine and the 5R55S transmission may exhibit a harsh downshift when coming to a stop.
The fix involves a PCM reprogramming to the latest calibration using IDS release 72.04 or higher and 73.01 or higher.
The vehicle is equipped with an adaptive transmission shift strategy which allows the computer to learn the transmission’s unique parameters and improve shift quality. When the adaptive strategy is reset, the computer will begin a re-learning process.
This re-learning process may result in firmer-than-normal upshifts and downshifts for several days until the re-learn is complete.