World Transmission Wt Electronic Control System - PREVOST Le Mirage XL Owner's Manual

STARTING AND STOPPING PROCEDURES
Note:
Engine brake is operative only when ac-
celerator pedal is released, and when engine
speed is over 900 rpm.
Each time the engine brake system is in opera-
tion, the stoplights will automatically light up.
World Transmission WT Elec-
tronic Control System
The WT Electronic Control System consists of
five (5) major components connected by wiring
harnesses - Electronic Control Unit (ECU), direct
electronic communication, three (3) speed sen-
sors, push-button shifter, and control module
(which contains solenoid valves and a pressure
switch). The throttle position sensor, speed sen-
sors pressure switch, and push-button shifter
transmit information to the ECU. The ECU pro-
cesses this information and sends signals to ac-
tuate specific solenoids located on the control
module in the transmission.
control both the oncoming and offgoing clutch
pressure during a shift.
Another feature of the World Transmission is its
ability to adapt or "learn" as it operates. Each
shift is electronically measured, stored and used
by the ECU to adapt and "learn" the optimum
conditions for future clutch apply and release. It
is important to note that if the shift quality of low
mileage vehicles or vehicles with new or recali-
brated ECU's is unacceptable, simply drive the
vehicle through its shift ranges for awhile. After
this "learning" period any rough shifting will be
corrected and shift quality will be restored.
In addition to controlling the operation of the
transmission, the ECU monitors the system for
conditions that could result in damage to the
transmission or improper vehicle operation.
When one of these conditions is detected, the
ECU is programmed to respond automatically in
a manner which will ensure safe operation of the
vehicle and the transmission.
Torque Converter
The torque converter consists of three (3) ele-
ments - pump, turbine, and stator. The pump is
the input element and is driven directly by the
engine. The turbine is the output element and is
hydraulically driven by the pump. The stator is
the reaction (torque multiplying) element. When
the pump turns faster than the turbine, the
These solenoids
4 - 4
torque converter is multiplying torque. When the
turbine approaches the speed of the pump, the
stator starts to rotate with the pump and turbine.
When this occurs, torque multiplication stops
and the torque converter functions as a fluid
coupling.
The lockup clutch is located inside the torque
converter and consists of three (3) elements -
piston, clutch plate/damper, and backplate. The
piston and backplate are driven by the engine.
the clutch plate/damper, located between the
piston and backplate, is splined to the converter
turbine. The lockup clutch is engaged and re-
leased in response to electronic signals from the
ECU. Engagement of the lockup clutch provides
a direct drive from the engine to the transmission
gearing. This eliminates converter slippage to
provide maximum fuel economy. The torsional
damper absorbs engine torsional vibration.
The lockup clutch releases at lower speeds and
when ECU detects conditions requiring it to be
released.
Planetary Gears and Clutches
A series of three (3) helical planetary gear sets
and shafts provides the gear ratios and direction
of travel for the vehicle. The planetary gear sets
are controlled by five (5) multiplate clutches that
work in pairs to produce six (6) speeds. The
clutches are applied and released hydraulically in
response to electronic signals from the ECU to
the appropriate combination of solenoids.
Cooler Circuit
The transmission oil is cooled by a remote-
mounted oil cooler. Connections to the cooling
circuit are located at the rear of the transmission
to facilitate installation of remote cooler lines. Oil
ports are internal requiring only coolant to be
routed to and from the cooler.