STARTING AND DRIVING
ALLISON TRANSMISSION
Preselects for your transmission
model
As an option, the preselect shift points
during engine brake operation can be
specied to be the same schedule
selected when the TCM is programmed
by the vehicle OEM for non-engine
brake operation:
• Standard Preselects – downshifts
occur so the engine speed after the
shift is approximately 300 rpm above
the engine governed speed
• Low Preselects – downshifts occur
so the engine speed after the shift is
approximately 150 rpm above the
engine governed speed
NOTE
Specify Standard or Low Preselects when
the TCM is programmed.
The preselect schedule chosen above
will be activated for downshifts that
occur while the engine brake is active
and until operation in a specied gear is
reached. This specied gear is the
Engine Brake Preselect Range Customer
Modiable Constant (CMC) that is
programmable using Universal Allison
DOC
®
. If this CMC is set to a value
higher than 2nd gear, then downshifts
from the Engine Brake Preselect Range
to 2nd gear will be made as standard
(nonengine brake) closed throttle
downshifts. Additionally, if the TCM is
programmed to make engine brake
preselect downshifts at Standard
Preselects or Low Preselects speeds,
downshifts between the Engine Brake
Preselected Range to an even lower
gear can be specied to use the
Alternate Engine Brake Preselect
downshift speeds. The lowest gear to
use this downshift schedule is also a
CMC (Alternate Engine Brake Preselect
Range). If this option is specied and the
Alternate Engine Brake Preselect Range
CMC is higher than 2nd gear, downshifts
from the Alternate Engine Brake
Preselect Range to 2nd gear uses
normal (nonpreselect) closed throttle
shift speeds.
NOTE
If an exhaust brake or engine compression
brake is installed on the engine, then they
must be integrated to the transmission
controls. Shift quality issues will arise if
not properly integrated to the transmission
controls.
Retarder Mode
The retarder mode shift schedule is
automatically activated when the
retarder is switched on in order to raise
closed throttle downshifts for additional
cooling during retarder operation.
Retarder closed throttle downshifts
occur at speeds approximately halfway
between the normal closed throttle
downshift and the preselect downshift
for each range.
Accelerator Control
The position of the accelerator pedal
inuences when automatic shifting
occurs. An electronic throttle position
signal tells the Transmission Control
Module (TCM) how much the operator
has pressed the pedal. When the pedal
is fully pressed, upshifts occur
automatically at higher engine speeds. A
partially pressed position of the pedal
causes upshifts to occur at lower engine
speeds.
Kickdown
Kickdown is an optional shift schedule
which is activated when the kickdown
input function is enabled. If shift
schedule S2, S3, or S4 is in use and
kickdown is active, all shifts revert to
schedule S1, Wide Open Throttle (WOT)
shift points. Similarly, if shift schedule
S6, S7, or S8 is in use and kickdown is
active, all shifts revert to schedule S5,
WOT shift points.
Avoid transmission performance issues
by contacting an Allison Transmission
distributor or dealer when one of these
conditions occur:
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X Publication_PC28
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