Dodge Durango (DN). Manual — part 117
STATOR
The stator assembly (Fig. 5) is mounted on a sta-
tionary shaft which is an integral part of the oil
pump. The stator is located between the impeller and
turbine within the torque converter case (Fig. 6). The
stator contains an over-running clutch, which allows
the stator to rotate only in a clockwise direction.
When the stator is locked against the over-running
clutch, the torque multiplication feature of the torque
converter is operational.
TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 7) was installed to improve the effi-
ciency of the torque converter that is lost to the slip-
page of the fluid coupling. Although the fluid
coupling provides smooth, shock–free power transfer,
it is natural for all fluid couplings to slip. If the
impeller
and
turbine
were
mechanically
locked
together, a zero slippage condition could be obtained.
A hydraulic piston was added to the turbine, and a
friction material was added to the inside of the front
cover to provide this mechanical lock-up.
OPERATION
The converter impeller (Fig. 8) (driving member),
which is integral to the converter housing and bolted
to the engine drive plate, rotates at engine speed.
The converter turbine (driven member), which reacts
from fluid pressure generated by the impeller, rotates
and turns the transmission input shaft.
TURBINE
As the fluid that was put into motion by the impel-
ler blades strikes the blades of the turbine, some of
the energy and rotational force is transferred into the
turbine and the input shaft. This causes both of them
(turbine and input shaft) to rotate in a clockwise
direction following the impeller. As the fluid is leav-
ing the trailing edges of the turbine’s blades it con-
tinues in a “hindering” direction back toward the
impeller. If the fluid is not redirected before it strikes
Fig. 4 Turbine
1 – TURBINE VANE
2 – ENGINE ROTATION
3 – INPUT SHAFT
4 – PORTION OF TORQUE CONVERTER COVER
5 – ENGINE ROTATION
6 – OIL FLOW WITHIN TURBINE SECTION
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DESCRIPTION AND OPERATION (Continued)
the impeller, it will strike the impeller in such a
direction that it would tend to slow it down.
STATOR
Torque multiplication is achieved by locking the
stator’s over-running clutch to its shaft (Fig. 9).
Under stall conditions (the turbine is stationary), the
oil leaving the turbine blades strikes the face of the
stator blades and tries to rotate them in a counter-
clockwise direction. When this happens the over–run-
ning clutch of the stator locks and holds the stator
from rotating. With the stator locked, the oil strikes
the stator blades and is redirected into a “helping”
direction before it enters the impeller. This circula-
tion of oil from impeller to turbine, turbine to stator,
and stator to impeller, can produce a maximum
torque multiplication of about 2.4:1. As the turbine
begins to match the speed of the impeller, the fluid
that was hitting the stator in such as way as to
cause it to lock–up is no longer doing so. In this con-
dition of operation, the stator begins to free wheel
and the converter acts as a fluid coupling.
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and
turbine are rotating at about the same speed and the
stator is freewheeling, providing no torque multipli-
cation. By applying the turbine’s piston to the front
cover’s friction material, a total converter engage-
ment can be obtained. The result of this engagement
is a direct 1:1 mechanical link between the engine
and the transmission.
Fig. 5 Stator Components
1 – CAM (OUTER RACE)
2 – ROLLER
3 – SPRING
4 – INNER RACE
Fig. 6 Stator Location
1 – STATOR
2 – IMPELLER
3 – FLUID FLOW
4 – TURBINE
Fig. 7 Torque Converter Clutch (TCC)
1 – IMPELLER FRONT COVER
2 – THRUST WASHER ASSEMBLY
3 – IMPELLER
4 – STATOR
5 – TURBINE
6 – FRICTION DISC
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DESCRIPTION AND OPERATION (Continued)
Converter clutch engagement in third or fourth
gear range is controlled by sensor inputs to the pow-
ertrain control module. Inputs that determine clutch
engagement are: coolant temperature, engine rpm,
vehicle speed, throttle position, and manifold vac-
uum. The torque converter clutch is engaged by the
clutch solenoid on the valve body. The clutch can be
engaged in third and fourth gear ranges depending
on overdrive control switch position. If the overdrive
control switch is in the normal ON position, the
clutch will engage after the shift to fourth gear, and
above approximately 72 km/h (45 mph). If the control
switch is in the OFF position, the clutch will engage
after the shift to third gear, at approximately 56
km/h (35 mph) at light throttle.
ELECTRONICALLY MODULATED CONVERTER
CLUTCH ENGAGEMENT
DESCRIPTION
In order to reduce heat build-up in the transmis-
sion and buffer the powertrain against torsional
vibrations, the TCM can duty cycle the L/R-CC Sole-
noid to achieve a smooth application of the torque
converter clutch. This function, referred to as Elec-
tronically Modulated Converter Clutch (EMCC) can
occur at various times depending on the following
variables:
• Shift lever position
• Current gear range
• Transmission fluid temperature
Fig. 8 Torque Converter Fluid Operation
1 – APPLY PRESSURE
2 – THE PISTON MOVES SLIGHTLY FORWARD
3 – RELEASE PRESSURE
4 – THE PISTON MOVES SLIGHTLY REARWARD
Fig. 9 Stator Operation
1 – DIRECTION STATOR WILL FREE WHEEL DUE TO OIL
PUSHING ON BACKSIDE OF VANES
2 – FRONT OF ENGINE
3 – INCREASED ANGLE AS OIL STRIKES VANES
4 – DIRECTION STATOR IS LOCKED UP DUE TO OIL PUSHING
AGAINST STATOR VANES
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DESCRIPTION AND OPERATION (Continued)
• Engine coolant temperature
• Input speed
• Throttle angle
• Engine speed
OPERATION
The TCM controls the torque converter by way of
internal logic software. The programming of the soft-
ware provides the TCM with control over the L/R-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 transmission or because the
TCM does not see the need for EMCC under current
driving 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 and 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 transmission input speed rela-
tive 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 (Fig. 10) is located at the front of the
transmission inside the bell housing and behind the
transmission front cover. The oil pump consists of two
independent pumps (Fig. 11), a number of valves (Fig.
12), a front seal (Fig. 13), and a bolt on reaction shaft.
The converter clutch switch and regulator valves, pres-
sure regulator valve, and converter pressure limit valve
are all located in the oil pump housing.
OPERATION
As the torque converter rotates, the converter hub
rotates the oil pump drive gear. As the drive gear
rotates both driven gears, the clearance between the
gear teeth increases in the crescent area, and creates
a suction at the inlet side of the pump. This suction
draws fluid through the pump inlet from the oil pan.
As the clearance between the gear teeth in the cres-
cent area decreases, it forces pressurized fluid into
the pump outlet and to the oil pump valves.
At low speeds, both pumps supply fluid to the trans-
mission. As the speed of the torque converter increases,
the pressure output of both pumps increases until the
primary pump pressure reaches the point where it can
close off the check valve located between the two
pumps. When the check valve is closed, the secondary
pump is shut down and the primary pump supplies all
the fluid to the transmission.
Fig. 10 Oil Pump
Fig. 11 Oil Pump Gears
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DESCRIPTION AND OPERATION (Continued)
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