A BRIEF DESCRIPTION OF THE ALLISON EMERGENCY
VEHICLE SERIES TRANSMISSIONS
Included in the Allison On-Highway Transmission family are the Emergency
Vehicle Series transmissions. The transmissions described in this manual include:
• WTEC III Controls or Allison 4
th
Generation Controls
• A torque converter with lockup and torsion damper
• Three planetary gear sets (four for 4700/4800 EVS)
A provision to mount a Power Takeoff (PTO) is available on all transmissions.
The integral retarder feature is optional.
ELECTRONIC CONTROL SYSTEM
All Emergency Vehicle Series transmissions come standard with WTEC III
Controls or Allison 4
th
Generation Controls. These systems consist of five major
components connected by OEM-furnished wiring harnesses. The five major
components are:
• Transmission Control Module (TCM) or Electronic Control Unit (ECU)
• Three speed sensors
• Remote shift selector
• Control module (which contains solenoid valves, a pressure switch, and an
optional oil level sensor)
• Engine Electronic Control Module (ECM) or Engine Throttle Position
Sensor (TPS), if installed
The TCM/ECU receives information from the following:
• Throttle position sensor, if installed
• Speed sensors
• Pressure switch
• Shift selector
The TCM/ECU processes information and then sends signals to actuate specific
solenoids located in the control valve module. These solenoids control both
oncoming and offgoing clutch pressures to provide closed-loop shift control by
matching input rpm during a shift to a desired profile programmed into the
TCM/ECU.
17
To Next Page
Loading...
Need help?
General
