In the drive position, the transmission will initially go
into first range when drive is selected. As vehicle
speed increases, the transmission will upshift auto-
matically through each available range up to fourth
range or fifth range. As the vehicle slows, the trans-
mission will downshift automatically.
When going downhill, downshift to a lower transmis-
sion range to increase engine braking and to help
maintain control. The transmission has a feature to
prevent automatic upshifting above the lower range
selected. However, during downhill operation, the
transmission may upshift to the next higher range, if
the engine is exceeding its governed speed in the
lower range.
CAUTION
Do not idle in drive for more than 5 minutes. Ex-
tended idling in drive may cause transmission
overheating and damage. Always select PB (auto-
apply parking brake) or P (park) if time at idle is
longer than 5 minutes.
NOTE: The shift into drive may not succeed if a
range inhibitor is active. Check for illumination
of the RANGE INHIBIT indicator.
4 and 3 (Fourth and Third Ranges,
optional)
Use the fourth or third range for city traffic and for
braking on steep downgrades.
3 and 2 (Third and Second Ranges,
standard)
Use the third or second range for heavy city traffic
and for braking on steeper downgrades.
1 (First Range)
Use first range when pulling through mud or deep
snow, when maneuvering in tight spaces, or when
driving up or down very steep grades. First range
provides the vehicle with its maximum driving torque
and maximum engine braking effect.
NOTE: To have the transmission select these
ranges automatically, leave the selector lever in
D (drive).
Allison MD Series
Refer to the Allison website for additional information,
www.allisontransmission.com
.
Safety Precautions
WARNING
Do not leave the vehicle unattended with the en-
gine running. If you leave the vehicle and the en-
gine is running, the vehicle can move suddenly,
which could result in personal injury or property
damage.
On vehicles with MD series transmissions, do the
following steps if you have to leave the cab with the
engine running (for example, when checking the
transmission fluid):
1.
Bring the vehicle to a complete stop using the
service brake.
2.
Put the transmission in N (neutral).
3.
Ensure that the engine is at low idle (500 to 800
rpm).
4.
Apply the parking brake and emergency brakes,
and make sure they are properly engaged.
5.
Chock the rear tires and take any other steps
necessary to keep the vehicle from moving.
Operating Instructions, MD Series
The Allison MD transmission is electronically con-
trolled and comes with a push-button shift control
that provides five or six forward ranges and one re-
verse range. The push-button shift selector has an R
(reverse), an N (neutral), a D (drive), an up arrow, a
down arrow, a mode button, and a digital display.
New shift controls — known as "fourth generation" —
were introduced in mid-2006. They replaced the pre-
vious units that are commonly referred to as "WTEC
III". See
Fig. 8.1
and
Fig. 8.2
.
R (Reverse)
Press the R button to select reverse. The digital dis-
play will show R when reverse is selected. Always
bring the vehicle to a complete stop and let the en-
gine return to idle before shifting from a forward
range to reverse, or from reverse to a forward range.
Drivetrain
8.5
