2005 MERCEDES-BENZ SPRINTER Service Repair Manual

OPERATION - TRANSMISSION TEMPERATURE
SENSOR
The temperature of the transmission oil has a con-
siderable effect on the shifting time and therefore the
shift quality. By measuring the oil temperature, shift
operations can be optimized in all temperature
ranges. The transmission oil temperature sensor (1)
(Fig. 222) is switched in series with the park/neutral
contact. The temperature signal is transferred to the
TCM only when the dry-reed contact of the park/neu-
tral contact is closed in REVERSE or a forward gear
position.Refer to the Transmission Temperature Sensor
Specifications table (Fig. 223) for the relationship
between transmission temperature, sensor voltage,
and sensor resistance.
TORQUE CONVERTER
DESCRIPTION
The torque converter (Fig. 224) is a hydraulic
device that couples the engine crankshaft to the
transmission. The torque converter consists of an
outer shell with an internal turbine, a stator, an
overrunning clutch, an impeller and an electronically
applied converter clutch. The converter clutch pro-
vides reduced engine speed and greater fuel economy
when engaged. Clutch engagement also provides
reduced transmission fluid temperatures. The con-
verter clutch engages in third gear. The torque con-
verter hub drives the transmission oil (fluid) pump.
The torque converter is a sealed, welded unit that
is not repairable and is serviced as an assembly.
CAUTION: The torque converter must be replaced if
a transmission failure resulted in large amounts of
metal or fiber contamination in the fluid.
Fig. 220 Transmission Temperature Sensor
1 - TRANSMISSION TEMPERATURE SENSOR
Fig. 221 Park/Neutral Contact
1 - SHELL OF ELECTRIC CONTROL MODULE
2 - PLUNGER
3 - PERMANENT MAGNET
4 - DRY-REED CONTACT
Fig. 222 Transmission Temperature Sensor
1 - TRANSMISSION TEMPERATURE SENSOR
VAAUTOMATIC TRANSMISSION - NAG1 21 - 141
TEMPERATURE SENSOR/PARK-NEUTRAL CONTACT (Continued)

IMPELLER
The impeller (Fig. 225) 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 con-
verter 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.
TURBINE
The turbine (Fig. 226) 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.
STATOR
The stator assembly (Fig. 227) 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. 228).
The stator contains a freewheeling clutch, which
allows the stator to rotate only in a clockwise direc-
tion. When the stator is locked against the freewheel-
ing clutch, the torque multiplication feature of the
torque converter is operational.Fig. 223 Transmission Temperature Sensor
Specifications
Fig. 224 Torque Converter
1 - TURBINE
2 - IMPELLER
3-STATOR
4 - INPUT SHAFT
5 - STATOR SHAFT
21 - 142 AUTOMATIC TRANSMISSION - NAG1VA
TORQUE CONVERTER (Continued)

TORQUE CONVERTER CLUTCH (TCC)
The TCC (Fig. 229) 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 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:²Shift lever position
²Current gear range
²Transmission fluid temperature
²Engine coolant temperature
²Input speed
²Throttle angle
²Engine speed
OPERATION
The converter impeller (driving member), which is
integral to the converter housing and bolted to the
engine drive plate, rotates at engine speed. The con-
verter turbine (driven member), which reacts from
fluid pressure generated by the impeller, rotates and
turns the transmission input shaft.
Fig. 225 Impeller
1 - ENGINE FLEXPLATE 4 - ENGINE ROTATION
2 - OIL FLOW FROM IMPELLER SECTION INTO TURBINE
SECTION5 - ENGINE ROTATION
3 - IMPELLER VANES AND COVER ARE INTEGRAL
VAAUTOMATIC TRANSMISSION - NAG1 21 - 143
TORQUE CONVERTER (Continued)

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 ªhinderingº 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.
Fig. 226 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
Fig. 227 Stator Components
1 - CAM (OUTER RACE)
2 - ROLLER
3 - SPRING
4 - INNER RACE
21 - 144 AUTOMATIC TRANSMISSION - NAG1VA
TORQUE CONVERTER (Continued)

STATOR
Torque multiplication is achieved by locking the
stator's over-running clutch to its shaft (Fig. 230).
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 ªhelpingº
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. 228 Stator Location
1-STATOR
2 - IMPELLER
3 - FLUID FLOW
4 - TURBINEFig. 229 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
Fig. 230 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
VAAUTOMATIC TRANSMISSION - NAG1 21 - 145
TORQUE CONVERTER (Continued)

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 (Fig. 231) to the front cover, a total con-
verter engagement 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, fourth,
and fifth gear ranges.
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 torque
converter solenoid. There are four output logic states
that can be applied as follows:
²No EMCC
²Partial EMCC
²Full EMCC
²Gradual-to-no EMCCNO EMCC
Under No EMCC conditions, the TCC 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 TCC 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 TCC 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 TCC 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. The hub must be smooth to avoid damaging the
pump seal at installation.
(1) Lubricate oil pump seal lip with transmission
fluid.
Fig. 231 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
21 - 146 AUTOMATIC TRANSMISSION - NAG1VA
TORQUE CONVERTER (Continued)

(2) Place torque converter in position on transmis-
sion.
CAUTION: Do not damage oil pump seal or con-
verter hub 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.
(6) Check converter seating with a scale and
straightedge (Fig. 232). Surface of converter lugs
should be at least 19 mm (3/4 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.
TORQUE CONVERTER HUB
SEAL
REMOVAL
(1) Remove the torque converter (Refer to 21 -
TRANSMISSION/AUTOMATIC - NAG1/TORQUE
CONVERTER - REMOVAL).
(2) Remove the torque converter hub seal with
suitable screw and slide hammer.
INSTALLATION
(1) Position the torque converter hub seal (Fig.
233) over the input shaft and against the transmis-
sion oil pump.
(2) Using Seal Installer 8902A (Fig. 234), install a
new torque converter hub seal.
(3) Install the torque converter (Refer to 21 -
TRANSMISSION/AUTOMATIC - NAG1/TORQUE
CONVERTER - INSTALLATION).
Fig. 232 Torque Converter Installation Depth
1 - TORQUE CONVERTER
2 - TRANSMISSION HOUSING
Fig. 233 Position Torque Converter Hub Seal
1 - TORQUE CONVERTER HUB SEAL
2 - INPUT SHAFT
Fig. 234 Install Torque Converter Hub Seal
1 - OIL PUMP
2 - SEAL INSTALLER 8902A
VAAUTOMATIC TRANSMISSION - NAG1 21 - 147
TORQUE CONVERTER (Continued)