WORKHORSE CUSTOM CHASSIS
Service Manual
Automatic Transmission – Allison
2007 W Series
© 2006 Workhorse Custom Chassis — All Rights Reserved
SECTION
7.2
PAGE
55
2007 W Series Chassis
WSM082106
TRANSMISSION COMPONENT AND SYSTEM
DESCRIPTION
Engine/Transmission Connection
The converter housing of 1000 Series transmissions
mates directly to the engine block. Flexplate drive is
used for engine-to-transmission torque transfer.
Torque Converter
Several torque converters are available to match the
transmissions to a wide variety of diesel and gasoline
engines. The torque converter is a single-stage,
polyphase, and 3-element unit, consisting of a pump,
stator, and turbine. At lower output speeds, the torque
converter multiplies torque and provides a fl uid coupling
to the engine. At higher speeds, the torque converter
clutch (TCC) is automatically engaged to provide direct
drive from the engine to the transmission. Hydraulic fl uid
for converter charging pressure comes from the sump
and is supplied by the input pump. The TCC is applied
or released by changing direction of fl uid in the torque
converter. An integral converter damper minimizes the
need for additional engine vibration control.
Gear Sets
The planetary gear train includes 3 constant-mesh
planetary gear sets containing high-helix gears. By the
engagement of the clutches in various combinations, the
planetary sets act singly or together to provide 6 forward
ranges, NEUTRAL, and REVERSE.
Clutches
5 clutches, 2 rotating and 3 stationary, direct the fl ow
of torque through the transmission. All range clutches
are hydraulically actuated and spring-released, with
automatic wear compensation. The transmission fl uid
cools the clutches. The transmission control module
(TCM) signals solenoid valves to apply and release
clutches based on speed and power combinations and
the range selected by the operator.
Hydraulic System
A common hydraulic system serves the torque converter
and the transmission. Transmission fl uid for all hydraulic
operations, lubrication, and cooling comes from the
sump and is supplied by the charging pump.
Transmission Fluid Filtration
Fluid fi ltration is provided by 2 fi lter systems. A suction
fi lter, located in the sump, provides general protection to
the entire hydraulic system by fi ltering large particulates.
A spin-on fi lter provides full-time protection for the
control solenoids and multipass protection for the
entire system. The spin-on fi lter is externally located
on the converter housing at the lower left front of the
transmission.
