Mercury 1999 Mountaineer Owner's Manual page 151

Drive – Not shown on the display. Activate by pressing the transmission
control switch on the end of the gearshift lever with the gearshift in the
position. The TCIL will illuminate on the instrument cluster.
Transmission operates in gears one through four.
more engine braking than
conditions (i.e., city traffic, hilly terrain, etc.) cause the transmission to
excessively shift between
(Overdrive) when:
driving with a heavy load
towing a trailer up or down steep hills
additional engine braking is desired. If towing a trailer, refer to
Driving while you tow in the Trailer Towing chapter.
To return to (Overdrive) mode, press the transmission control switch.
The TCIL will no longer be illuminated.
Each time the vehicle is started, the transmission will automatically
return to normal overdrive mode.
2 (Second)
Use 2 (Second) to start-up on
slippery roads or to provide
additional engine braking on
downgrades. Transmission operates
in third gear.
1 (First)
Use 1 (First) to provide maximum
engine braking on steep
downgrades. Upshifts can be made
by shifting to 2 (Second) or to
(Overdrive). Selecting 1 (Low)
at higher speeds causes the transmission to shift to a lower gear and will
shift to 1 (First) after the vehicle decelerates to the proper vehicle
speed.
(Overdrive) and is useful whenever driving
(Overdrive) and (Drive). Also deactivate
Driving
(Drive) provides
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