WORKHORSE CUSTOM CHASSIS
Service Manual
2007 W Series
SECTION
7.2
PAGE
60
Automatic Transmission – Allison
2007 W Series Chassis
© 2006 Workhorse Custom Chassis — All Rights Reserved
WSM082106
Speed Sensors
IMPORTANT:
Do not rotate the sensor in the retaining bracket.
Do not rotate the sensor in the retaining bracket.
Changing the sensor/bracket orientation may cause
Changing the sensor/bracket orientation may cause
improper operation.
improper operation.
There are 3 speed sensors typically required for use
with 1000 Series transmissions. They include the engine
speed sensor, the turbine speed sensor, and the output
speed sensor. The speed sensors provide revolutions
per minute (RPM) information to the TCM. The speed
ratios between the various sensors allow the TCM to
determine the transmission operating range. Speed
sensor information is also used to control the timing of
clutch apply pressures, resulting in the best possible
shift quality. Hydraulic conditions are detected by
comparing the speed sensor information for the current
range, to the range of the speed sensor information
stored in TCM memory. The speed sensors are variable
reluctance devices that convert mechanical motion to an
AC voltage. Each sensor consists of a wire coil wrapped
around a pole piece that is adjacent to a permanent
magnet. These elements are contained in a housing that
is mounted adjacent to a rotating ferrous member.
Shift Selector
The vehicle is equipped with a column type shift
selector. In addition to the column shifter, another
component associated with the shift selector is the
internal mode switch (IMS), which is mounted internally
on the selector shaft. The IMS transmits selector
position information to the TCM. The IMS detects
the angular position of the shift selector shaft. This
