General Information, Allison Transmissions
Refer to the Allison website for additional information,www.allisontransmission.com.
HD-series automatic transmissions have six forward speeds and one reverse speed. These transmissions have electronic shift controls that can be programmed to allow the use of different numbers of geared speeds. For instance, the transmission can be programmed to operate as a 4-speed, 5-speed, or 6-speed unit in the "primary" shift mode. If needed, a "secondary" shift mode can be programmed to provide another shift configuration to optimize vehicle use under different operating conditions. To activate a secondary shift mode, or other special functions programmed into the electronic control unit (ECU), depress the Mode button. See Fig.. "Mode On" is displayed in the indicator panel just above the push buttons. A label just above the Mode button identifies the special function.
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Indicator Panel
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Mode ID
Fig. 1, Allison Push Button Shift Selector
Note: Each time a push button is depressed on the shift selector, a short beep will be heard. This indicates that the ECU has received input to change operation.
The HD-series transmission is designed to warn the driver of transmission malfunctions. The driver should know the extent of the warning system in order to safely operate the vehicle.