WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
68
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
3 and the manual selector valve to the 1-2-3-4 clutch,
keeping the 1-2-3-4 clutch applied. The combination
of the 1-2-3-4 clutch and the low and reverse clutch
application allows the transmission to stay in fi rst range
for limp home capability.
If electrical power is interrupted while the transmission
is in fi rst range, moving the manual selector valve to
Neutral (N) will cut off main pressure to the 1-2-3-4
clutch and the clutch will be exhausted. The low and
reverse clutch remains applied. Because only one clutch
is applied, the transmission goes to neutral.
If electrical power is interrupted while the transmission
is in fi rst range, moving the manual selector valve to
Reverse (R) cuts off main pressure to the 1-2-3-4 clutch,
exhausting the 1-2-3-4 clutch. The manual selector
valve directs main pressure through the TCC valve to
the bottom of shift valve 2, de-stroking the valve and
opening the path for main pressure to feed the low and
reverse clutch, keeping the clutch applied. PCS1 control
pressure is then directed to the 3rd, 5th, and reverse
clutch, applying the clutch. The combination of the 3rd,
5th, and reverse clutch and the low and reverse clutch
application produces Reverse (R) range operation, for
limp home capability.
IMPORTANT:
If the manual selector valve is put back in a forward
If the manual selector valve is put back in a forward
range after reverse has been attained, the selector
range after reverse has been attained, the selector
valve will direct fluid to the 1-2-3-4 clutch and shift valve
valve will direct fluid to the 1-2-3-4 clutch and shift valve
2 will stay de-stroked, directing fluid to the 3rd, 5th, and
2 will stay de-stroked, directing fluid to the 3rd, 5th, and
reverse clutch, resulting in third range operation.
reverse clutch, resulting in third range operation.
If electrical power is interrupted while the transmission is
in fi rst range, resulting in only fi rst, neutral, and reverse
operation, the engine may be shut down and restarted to
attain neutral, third, and reverse operation.
