WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
79
2007 W Series Chassis
WSM082106
Fifth Range
Before making a shift from fourth to fi fth range, the
transmission control module (TCM) makes certain all of
the shift valves are in the correct position with shift valve
1 and shift valve 3 stroked and shift valve 2 de-stroked.
Pressure control solenoid 2 (PCS2) is de-energized,
exhausting PCS2 signal pressure and pressure control
valve 2 de-strokes, which allows the 1-2-3-4 clutch to
exhaust through the manual selector valve, shift valve
3 and shift valve 1, and pressure control valve 2. PCS1
is de-energized, raising the PCS1 signal and pressure
control valve 1 pressures. PCS1 pressure is directed
through shift valve 2 to the 3rd, 5th, and reverse clutch,
applying the clutch. The TCM reduces the current to
PCS1, which controls the rate at which pressure control
valve 1 supplies pressure to the 3rd, 5th, and reverse
clutch, and reduces the current to PCS2, which controls
the rate at which pressure control valve 2 exhausts the
1-2-3-4 clutch, assuring a smooth transition from fourth
to fi fth range. The 4-5-6 clutch continues to be applied
by main pressure fl owing through shift valve 3, shift
valve 2, and the manual selector valve.
The combination of the 4-5-6 clutch and the 3rd, 5th,
and reverse clutch application produces fi fth range
operation.
Pressure switch 1 and pressure switch 2 are turned
OFF, providing feedback that shift valve 1 and shift valve
2 are in the de-stroked position, and pressure switch 3
remains ON, providing feedback that shift valve 3 is in
the stroked position.
If electrical power is interrupted while the transmission
is in fi fth range, PCS2, shift solenoid 3 (SS3), and
the torque converter clutch (TCC) solenoid (if TCC is
applied) de-energize. Although SS3 no longer supplies
control main pressure to the top of shift valve 3, control
main pressure fl ows through shift valve 1 to the top
of shift valve 3, keeping the valve stroked. Normally
closed PCS1 continues to block the exhaust of the
signal pressure (signal remains control main). The signal
pressure on top of pressure control valve 1 produces
maximum control pressure, which is routed through shift
valve 2 to the 3rd, 5th, and reverse clutch, keeping the
clutch applied. Main pressure feeds through shift valve 3
and shift valve 2 and the manual selector valve to the 4-
5-6 clutch, keeping the clutch applied.
The combination of the 4-5-6 clutch and the 3rd, 5th,
and reverse clutch application produces fi fth range
operation for limp home capability.
If the TCC is applied, the TCC solenoid de-energizes,
causing the TCC pressure control valve to de-stroke,
exhausting pressure from the top of the converter fl ow
valve. The converter fl ow valve de-strokes, redirecting
main overage to converter in and converter out fl ow to
the cooler. The TCC is now released.
If electrical power is interrupted while the transmission
is in fi fth range (causing fi fth range converter operation)
and the manual selector valve is moved to Neutral (N),
the 4-5-6 clutch exhausts through the manual selector
