A BRIEF DESCRIPTION OF THE ALLISON MOTORHOME
SERIES TRANSMISSIONS
Included in the Allison On-Highway Transmission family are the Motorhome
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
Motorhome Series transmissions may contain an integral retarder or a provision to
mount a Power Takeoff (PTO).
ELECTRONIC CONTROL SYSTEM
All Motorhome Series transmissions come standard with WTEC III Controls or
Allison 4
th
Generation Controls. These systems consist of
fi
ve major components
connected by OEM-furnished wiring harnesses. The
fi
ve 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 speci
fi
c
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 pro
fi
le programmed into the
TCM/ECU.
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