Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 471

IMPELLER

The impeller (3) (Fig. 243) is an integral part of

the converter housing. The impeller consists of
curved blades placed radially along the inside of the
housing on the transmission side of the converter. As
the converter housing is rotated by the engine, so is
the impeller, because they are one and the same and
are the driving members of the system.

Fig. 243 Impeller

1 - ENGINE FLEXPLATE

4 - ENGINE ROTATION

2 - OIL FLOW FROM IMPELLER SECTION INTO TURBINE SEC-
TION

5 - ENGINE ROTATION

3 - IMPELLER VANES AND COVER ARE INTEGRAL

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TURBINE

The turbine (1) (Fig. 244) is the output, or driven,

member of the converter. The turbine is mounted
within the housing opposite the impeller, but is not
attached to the housing. The input shaft is inserted
through the center of the impeller and splined into
the turbine. The design of the turbine is similar to
the impeller, except the blades of the turbine are
curved in the opposite direction.

Fig. 244 Turbine

1 - TURBINE VANE

4 - PORTION OF TORQUE CONVERTER COVER

2 - ENGINE ROTATION

5 - ENGINE ROTATION

3 - INPUT SHAFT

6 - OIL FLOW WITHIN TURBINE SECTION

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STATOR

The stator assembly (1-4) (Fig. 245) is mounted on

a stationary shaft which is an integral part of the oil
pump.

The stator (1) is located between the impeller (2)

and turbine (4) within the torque converter case (Fig.
246). The stator contains a freewheeling clutch,
which allows the stator to rotate only in a clockwise
direction. When the stator is locked against the free-

wheeling clutch, the torque multiplication feature of
the torque converter is operational.

TORQUE CONVERTER CLUTCH (TCC)

The TCC (9) (Fig. 247) was installed to improve

the efficiency of the torque converter that is lost to
the slippage 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 with friction material was added
to the turbine 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 torque con-
verter lock-up solenoid to achieve a smooth applica-
tion of the torque converter clutch. This function,
referred to as Electronically Modulated Converter
Clutch (EMCC) can occur at various times depending
on the following variables:

• Shift lever position

• Current gear range

Fig. 245 Stator Components

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

Fig. 246 Stator Location

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

Fig. 247 Torque Converter Lock-up Clutch

1 - TURBINE
2 - IMPELLER
3 - STATOR
4 - INPUT SHAFT
5 - STATOR SHAFT
6 - PISTON
7 - COVER SHELL
8 - INTERNALLY TOOTHED DISC CARRIER
9 - CLUTCH PLATE SET
10 - EXTERNALLY TOOTHED DISC CARRIER
11 - TURBINE DAMPER

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• Transmission fluid temperature

• Engine coolant temperature

• Input speed

• Throttle angle

• Engine speed

OPERATION

The converter impeller (driving member) (2) (Fig.

248), which is integral to the converter housing and
bolted to the engine drive plate, rotates at engine
speed. The converter turbine (driven member) (1),
which reacts from fluid pressure generated by the
impeller, rotates and turns the transmission input
shaft (4).

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. 249)
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 2.0:1. 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.

Fig. 248 Torque Converter

1 - TURBINE
2 - IMPELLER
3 - STATOR
4 - INPUT SHAFT
5 - STATOR SHAFT
6 - TURBINE DAMPER

Fig. 249 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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