WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
452
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
engages the low and reverse clutch to obtain REVERSE
and to learn the low and reverse clutch volume. The
TCM repeats this test until the volume learned for the
low and reverse clutch has converged.
IMPORTANT:
All shifts will be left in fast adaptive mode at this point.
All shifts will be left in fast adaptive mode at this point.
After learning the 1-2-3-4 and the low and reverse clutch
volume, FastLearn updates the adaptive volume data for
all shifts with either the 1-2-3-4 or the low and reverse
on-coming clutch.
Troubleshooting
If FastLearn will not run and the above stated conditions
have been met, ensure the following:
• Transmission fl uid temperature is between 40-100°C
(104-212°F).
• Closed throttle and engine at warm idle RPM
• No active DTCs
• All speed sensors are connected and functioning
properly.
• Internal mode switch is functioning properly
• Main pressure is within specifi cation.
• TCC slip speed less than 100 RPM at idle in PARK/
NEUTRAL
LIMP HOME MODE
Principle of Operation
The Allison transmission incorporates control logic that
enables the transmission to revert to a limited total
hydraulic operation. The hydraulic system provides a
Limp Home Mode, allowing the operator to drive the
vehicle to a service location. If power is interrupted
while the transmission is operating in R, REVERSE, or
N, NEUTRAL, the transmission defaults to or continues
NEUTRAL operations. The operator may turn off the
engine and start the engine again. The shift selector
provides REVERSE/NEUTRAL/DRIVE capability
regardless of the range where the failure occurred.
In this state, pressure control solenoid 1 (PCS1), de-
energized, allows the 3rd, 5th and reverse clutch to be
applied. If the selector valve is moved to the REVERSE
position, main pressure is routed to the low and reverse
clutch, allowing REVERSE operation. If the selector
valve is moved to the DRIVE position, main pressure
is routed to the 1-2-3-4 clutch, allowing THIRD range
operation.
Test Procedure
If a No Forward, No REVERSE, or Will Not Move
condition occurs:
1. Set the parking brake.
2. With the ignition OFF, disconnect the 80-way
connector at the transmission control module (TCM).
3. Using a fused jumper wire, connect terminal R of the
automatic transmission inline 20-way connector to a
known good ground.
4. Start the engine and move the range selector to
REVERSE position.
5. The transmission should engage REVERSE range.
