the coupling is produced by transmission fluid, the
turbine can slip or turn slower than the impeller.
The stator contains a one-way overrunning clutch,
which free-wheels when the impeller and turbine are
rotating at the same speed. However, the stator stops
when speed reduction or torque increase take place.
When the stator stops, it changes the direction of the
fluid leaving the turbine vanes. This directs fluid
back into the impeller with greater force, resulting in
torque multiplication.
The torque converter clutch is hydraulically oper-
ated and controlled by the TCM. It consists of a pis-
ton and a frictional disc that form a direct
mechanical link between the impeller and turbine
when slippage is inefficient or unnecessary.
The torque converter hub drives the transmission
oil pump.
ELECTRONICALLY MODULATED CONVERTER
CLUTCH
In order to reduce heat build-up in the transmis-
sion and buffer the powertrain against torsional
vibrations, the TCM can duty cycle the LR/CC sole-
noid to achieve a smooth application of the torque
converter clutch. This function, also referred as
“Electronically Modulated Converter Clutch (EMCC),
can occur at various times depending on the follow-
ing variables:
• Shift lever position
• Current gear range
• Transmission fluid temperature
• Engine coolant temperature
• Input speed
• Throttle angle
• Engine speed
The TCM controls the torque converter by way of
internal logic software. The programming of the soft-
ware provides the TCM with fine control over the
LR/CC solenoid. There are four output logic states
that can be applied as follows:
• No EMCC
• Partial EMCC
• Full EMCC
• Gradual-to-no EMCC
NO EMCC
Under No EMCC conditions, the L/R Solenoid is
OFF. There are several conditions that can result in
NO EMCC operations. No EMCC can be initiated
due to a fault in the transaxle or because the TCM
does not see the need for EMCC under current driv-
ing conditions.
PARTIAL EMCC
Partial EMCC operation modulates the L/R Sole-
noid (duty cycle) to obtain partial torque converter
clutch application. Partial EMCC operation is main-
tained until Full EMCC is called for an actuated.
During Partial EMCC some slip does occur. Partial
EMCC will usually occur at low speeds, low load and
light throttle situations.
FULL EMCC
During Full EMCC operation, the TCM increases
the L/R Solenoid duty cycle to full ON after Partial
EMCC control brings the engine speed within the
desired slip range of transaxle input speed relative to
engine rpm.
GRADUAL-TO-NO EMCC
This operation is to soften the change from Full or
Partial EMCC to No EMCC. This is done at mid-
throttle by decreasing the L/R Solenoid duty cycle.
OIL PUMP
DESCRIPTION
The oil pump is located in the pump housing inside
the bell housing of the transaxle case. The oil pump
consists of an inner and outer gear, a housing, and a
cover that also serves as the reaction shaft support.
Fig. 4 Oil Pump Assembly
1 – PUMP HOUSING
2 – OUTER PUMP GEAR
3 – INNER PUMP GEAR
4 – REACTION SHAFT SUPPORT
5 – SEAL RINGS (4)
6 – REACTION SHAFT
7 – CRESCENT
LH 42LE TRANSAXLE 21 - 5
DESCRIPTION AND OPERATION (Continued)
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