Ford 1997 Aerostar Manual page 176

When to use Drive
You will note there is not a drive position on
your gearshift indicator. However, you will find
a transmission control switch labeled
OVERDRIVE OFF located on the end of the
gearshift lever. With overdrive canceled and the
OVERDRIVE OFF illuminated, the transmission
will operate in gears one through four. This is
useful if you experience frequent
downshift/upshift conditions, when operating a
heavy load or in hilly terrain, or if additional
engine braking is useful. However, shift back to
j (Overdrive) whenever practical for optimum
powertrain cooling and fuel economy. This can
be accomplished by pushing the transmission
control switch again, to cancel the OVERDRIVE
OFF control and light.
When to use 2 (Second)
With the gearshift in the 2 (Second) position,
more engine braking is provided. Use the 2
(Second) position to drive up moderately steep
grades, to start up slippery roads, or to provide
moderate engine braking on downgrades. DO
NOT GO FASTER THAN 55 mph (88 km/h) IN
THIS GEARSHIFT POSITION.
When to use 1 (Low)
With the gearshift in the 1 (First) position,
maximum engine braking is provided. This
position provides 1 (First) gear operation only
with no automatic upshifts. To obtain upshifts,
the gearshift must be moved out of this position.
Use the 1 (First) position to drive up steep
grades or to provide maximum engine braking
on downgrades.
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