Dodge Dakota (R1). Manual - part 720

STATOR

The stator assembly (Fig. 109) 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. 110).
The stator contains an over-running clutch, which
allows the stator to rotate only in a clockwise direc-
tion. When the stator is locked against the over-run-
ning clutch, the torque multiplication feature of the
torque converter is operational.

TORQUE CONVERTER CLUTCH (TCC)

The TCC (Fig. 111) was installed to improve the

efficiency of the torque converter that is lost to the
slippage of the fluid coupling. Although the fluid cou-
pling 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 with friction material was added to the tur-
bine assembly to provide this mechanical lock-up.

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

• Engine coolant temperature

• Input speed

• Throttle angle

• Engine speed

Fig. 109 Stator Components

1 - CAM (OUTER RACE)
2 - ROLLER
3 - SPRING
4 - INNER RACE

Fig. 110 Stator Location

1 - STATOR
2 - IMPELLER
3 - FLUID FLOW
4 - TURBINE

Fig. 111 Torque Converter Clutch (TCC)

1 - IMPELLER FRONT COVER
2 - THRUST WASHER ASSEMBLY
3 - IMPELLER
4 - STATOR
5 - TURBINE
6 - PISTON
7 - FRICTION DISC

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TORQUE CONVERTER (Continued)

OPERATION

The converter impeller (Fig. 112) (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
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. 113).
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 and friction
material to the front cover, 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.

The clutch can be engaged in second, 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

Fig. 112 Torque Converter Fluid Operation - Typical

1 - APPLY PRESSURE

3 - RELEASE PRESSURE

2 - THE PISTON MOVES SLIGHTLY FORWARD

4 - THE PISTON MOVES SLIGHTLY REARWARD

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TORQUE CONVERTER (Continued)

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.

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.

REMOVAL

(1) Remove transmission and torque converter

from vehicle.

(2) Place a suitable drain pan under the converter

housing end of the transmission.

CAUTION: Verify that transmission is secure on the
lifting device or work surface, the center of gravity
of the transmission will shift when the torque con-
verter is removed creating an unstable condition.
The torque converter is a heavy unit. Use caution
when separating the torque converter from the
transmission.

(3) Pull the torque converter forward until the cen-

ter hub clears the oil pump seal.

(4) Separate the torque converter from the trans-

mission.

INSTALLATION

Check converter hub and drive flats for sharp

edges, burrs, scratches, or nicks. Polish the hub and
flats with 320/400 grit paper or crocus cloth if neces-
sary. Verify that the converter hub o-ring is properly
installed and is free from debris. The hub must be
smooth to avoid damaging the pump seal at installa-
tion.

(1) Lubricate oil pump seal lip with transmission

fluid.

(2) Place torque converter in position on transmis-

sion.

CAUTION: Do not damage oil pump seal or con-
verter hub o-ring while inserting torque converter
into the front of the transmission.

(3) Align torque converter to oil pump seal open-

ing.

(4) Insert torque converter hub into oil pump.
(5) While pushing torque converter inward, rotate

converter until converter is fully seated in the oil
pump gears.

Fig. 113 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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TORQUE CONVERTER (Continued)

(6) Check converter seating with a scale and

straightedge (Fig. 114). Surface of converter lugs
should be at least 13 mm (1/2 in.) to rear of straight-
edge when converter is fully seated.

(7) If necessary, temporarily secure converter with

C-clamp attached to the converter housing.

(8) Install the transmission in the vehicle.
(9) Fill the transmission with the recommended

fluid.

TRANSMISSION CONTROL
RELAY

DESCRIPTION

The relay is supplied fused B+ voltage, energized

by the TCM, and is used to supply power to the sole-
noid pack when the transmission is in normal oper-
ating mode.

OPERATION

When the relay is “off”, no power is supplied to the

solenoid pack and the transmission is in “limp-in”
mode. After a controller reset, the TCM energizes the
relay. Prior to this, the TCM verifies that the con-
tacts are open by checking for no voltage at the
switched battery terminals. After this is verified, the
voltage at the solenoid pack pressure switches is
checked. After the relay is energized, the TCM mon-
itors the terminals to verify that the voltage is
greater than 3 volts.

TRANSMISSION RANGE
SENSOR

DESCRIPTION

The Transmission Range Sensor (TRS) is mounted

to the top of the valve body inside the transmission.

The Transmission Range Sensor (TRS) has six

switch contacts that:

• Determine shift lever position

• Supply ground to the Starter Relay in Park and

Neutral only.

• Supply ground to the TCM for backup lamp con-

trol in Reverse only.

The TRS also has an integrated temperature sen-

sor (thermistor) that communicates transmission
temperature to the TCM and PCM.

OPERATION

The Transmission Range Sensor (TRS) communi-

cates shift lever position to the TCM as a combina-
tion of open and closed switches. Each shift lever
position has an assigned combination of switch states
(open/closed) that the TCM receives from four sense
circuits. The TCM interprets this information and
determines the appropriate transmission gear posi-
tion and shift schedule.

There are many possible combinations of open and

closed switches (codes). Seven of these possible codes
are related to gear position and five are recognized
as “between gear” codes. This results in many codes
which

should

never

occur.

These

are

called

“invalid” codes. An invalid code will result in a DTC,
and the TCM will then determine the shift lever
position based on pressure switch data. This allows
reasonably normal transmission operation with a
TRS failure.

GEAR

Park

Temp 1

Reverse

Temp 2

Neutral 1

Neutral 2

Temp 3

Drive

Temp 4

Manual 2

Temp 5

Manual 1

Fig. 114 Checking Torque Converter Seating-Typical

1 - SCALE
2 - STRAIGHTEDGE

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TORQUE CONVERTER (Continued)

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