WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
58
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
TRANSMISSION INDICATORS AND MESSAGES
NORMAL Inhibits Which Result in a Blinking PRNDL
High engine speed NEUTRAL to Range shifts : When a
NEUTRAL to DRIVE or NEUTRAL to REVERSE shift is
made, when engine RPM is high, the shift is inhibited to
NEUTRAL. The TCM has torque management capability
and attempts to slow the engine to a point where it
makes the requested shift.
High Throttle or Torque Direction Change Shifts:
REVERSE to DRIVE, DRIVE to REVERSE, NEUTRAL
to DRIVE, and NEUTRAL to REVERSE shifts, where
throttle position is greater than 25 percent, are inhibited
to NEUTRAL. The TCM has torque management
capability and attempts to slow the engine to a point
where it makes the requested shift.
High Output Speed Direction Change Shifts : REVERSE
to DRIVE, DRIVE to REVERSE, and NEUTRAL to
REVERSE shifts, initiated above 300 RPM output speed
are inhibited to NEUTRAL.
Low Automatic Transmission Fluid (ATF) Level Low: Low
ATF level is caused by insuffi cient transmission fl uid
and lack of initial pump prime, caused by refi lling the
transmission.
Extremely Low ATF temperature: A shift out of
NEUTRAL when the ATF temperature is below -45°C (-
49°F) may be inhibited.
MALFUNCTIONS Which May Cause a Blinking PRNDL
Failure to detect turbine speed pull-down during a shift
may occur under the following conditions:
• A clutch is failed and the transmission cannot attain
the requested range.
• Invalid gear ratio
• Pressure control solenoid failure
• Turbine or output speed sensor failure
• Lack of pressure at startup
Conditions Which May Cause a BLANK PRNDL
The PRNDL display may be blank because of failure of
the internal mode switch circuits A, B, C, or P.
The transmission will command the most appropriate
range, based on reverse pressure switch and the
remaining internal mode switch inputs.
