2005 MERCEDES-BENZ SPRINTER engine

Shift Pressure (p-S)
The shift pressure is determined by the shift pres-
sure regulating solenoid valve and the shift pressure
regulating valve. The shift pressure:
²Regulates the pressure in the activating shift
element during the shift phase.
²Determines together with the modulating pres-
sure the pressure reduction at the deactivating shift
element as regulated by the overlap regulating valve.
²Initializes 2nd gear in limp-home mode.
Modulating Pressure (p-Mod)
The modulating pressure influences the size of the
working pressure and determines together with the
shift pressure the pressure regulated at the overlap
regulating valve. The modulating pressure is regu-
lated at the modulating pressure regulating solenoid
valve, which is under regulating valve pressure. The
modulating pressure is variable and relative to the
engine load.Regulating Valve Pressure (p-RV)
The regulating valve pressure is regulated at the
regulating valve pressure regulating valve in relation
to the working pressure (p-A) up to a maximum pres-
sure of 8 bar (116 psi). It supplies the modulating
pressure regulating solenoid valve, the shift pressure
regulating solenoid valve and the shift valve pressure
regulating valve.
Shift Valve Pressure (p-SV)
The shift valve pressure (p-SV) is derived from the
regulating valve pressure (p-RV), is regulated at the
shift valve pressure regulating valve and is then
present at the:
²1-2 and 4-5 shift solenoid valve.
²3-4 shift solenoid valve.
²2-3 shift solenoid valve.
²Torque converter lockup solenoid valve.
²3-4 and 2-3 shift pressure shift valve.
The shift valve pressure (p-SV) controls the com-
mand valves via the upshift/downshift solenoid
valves.
Overlap Pressure (p-š)
The overlap pressure controls the shift component
pressure reduction during a shift phase. The pres-
sure in a shift element as it disengages is controlled
during the shift phase depending on engine load
(modulating pressure) and the pressure in the shift
element as it engages. The adjusted pressure is
inversely proportional to the transmission capability
of the shift element being engaged (controlled over-
lap).
Working Pressure Regulating Valve (Operating Pressure)
The working pressure regulating valve (Fig. 89) is
located in the valve housing of the shift plate. It reg-
ulates the primary pressure of the hydraulic system.
Torque Converter Lockup Clutch Regulating Valve
The torque converter lock-up clutch regulating
valve (Fig. 90) is located in the valve housing of the
electrohydraulic control module. The valve is respon-
sible for the hydraulic control of the torque converter
lockup clutch and distribution of the lubricating oil.
Overlap Regulating Valve
Each shift group is assigned one overlap regulating
valve (Fig. 91). The 1-2 / 4-5 overlap regulating valve
is installed in the shift valve housing; the 2-3 and 3-4
overlap regulating valves are installed in the valve
housing. The overlap regulating valve regulates the
pressure reduction during a shift phase.
Fig. 88 Electrical Control Unit
1 - N3 SPEED SENSOR
2 - PLUG CONNECTOR
3 - MODULATING PRESSURE REGULATING SOLENOID
4 - SHIFT PRESSURE REGULATING SOLENOID
5 - 1-2/4-5 SHIFT SOLENOID
6 - 3-4 SHIFT SOLENOID
7 - ELECTRICAL CONTROL UNIT
8 - TRANSMISSION TEMPERATURE SENSOR
9 - STARTER INTERLOCK CONTACT
10 - 2-3 SHIFT SOLENOID
11 - TORQUE CONVERTER LOCK-UP SOLENOID
12 - N2 SPEED SENSOR
VAAUTOMATIC TRANSMISSION - NAG1 21 - 83
ELECTROHYDRAULIC UNIT (Continued)

Overlap Regulating Valve
During the shift phase the pressure (Fig. 102) in
the deactivating shift actuator is regulated in rela-
tion to the engine load (modulating pressure) and the
pressure in the activating actuator. The regulated
pressure is inversely proportional to the transfer
capacity of the activating shift actuator (regulated
overlap).
Command Valve
When the end face is unpressurized (stationary
phase), the working pressure is directed to the actu-
ated shift element. If the end face of the commandvalve (Fig. 103) is subjected to the shift valve pres-
sure (p-SV) (shift phase), then the shift pressure is
switched to the activating element and the overlap
pressure is switched to the deactivating element.
Shift Valve Holding Pressure
The holding pressure shift valve (Fig. 104) is actu-
ated by the pressures present at the end face in the
actuators and a spring. It assigns the working pres-
sure to the actuator with the higher pressure (taking
into account the spring force and the effective surface
area). The other element of the shift group is then
unpressurized. The valve switches over only during
the shift phase and only at a certain pressure ratio
between the overlap pressure (p-š) and the shift
pressure (p-S).
Shift Pressure Shift Valve
When the multiple-disc brake B1 (3) is activated,
the working pressure (pa) is applied to the end face
of the 1-2 / 4-5 shift pressure shift valve (4) (Fig. 105)
via the command valve (1). Its shift state is main-
tained during the shift phase by substituting the
shift element pressure acting on its end face (and
which is variable during the shift phase) with a cor-
responding constant pressure. When the multi-plate
clutch K1 (2) is activated, the end face of the shift
valve is unpressurized during the stationary and
shift phases, so the shift state is maintained during
the shift phase in this case too.
Fig. 103 Command Valve
1 - HOLDING CLUTCH B1
2 - DRIVING CLUTCH K13 - 1-2/4-5 COMMAND VALVE
Fig. 102 Overlap Regulating Valve
1 - OVERLAP REGULATING VALVE
2 - ANNULAR SURFACE ON OVERLAP REGULATING VALVE
VAAUTOMATIC TRANSMISSION - NAG1 21 - 89
ELECTROHYDRAULIC UNIT (Continued)

DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air
along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve and clutch operation. Foaming also causes fluid
expansion which can result in fluid overflow from the
transmission vent or fill tube. Fluid overflow can eas-
ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has three primary causes.
(1) Internal clutch slippage, usually caused by low
line pressure, inadequate clutch apply pressure, or
clutch seal failure.
(2) A result of restricted fluid flow through the
main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.
(3) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²overheat that generates sludge (fluid break-
down)
²failure to replace contaminated converter after
repair
The use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failuredue to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease and
other foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The torque converter should be replaced whenever
a failure generates sludge and debris. This is neces-
sary because normal converter flushing procedures
will not remove all contaminants.
STANDARD PROCEDURE
STANDARD PROCEDURE - CHECK OIL LEVEL
(1) Verify that the vehicle is parked on a level sur-
face.
(2) Remove locking pin (1) (Fig. 136). Remove the
plate of the locking pin with a suitable tool and press
out the pin remaining in the cap downwards.
(3) Remove cap (2).
WARNING: Risk of accident from vehicle starting off
by itself when engine running. Risk of injury from
contusions and burns if you insert your hands into
the engine when it is started or when it is running.
Secure vehicle to prevent it from moving off by
itself. Wear properly fastened and close-fitting work
clothes. Do not touch hot or rotating parts.
Fig. 136 Remove Dipstick Tube Cap Lock
1 - LOCKING PIN
2 - TUBE CAP
3 - DIPSTICK TUBE
21 - 102 AUTOMATIC TRANSMISSION - NAG1VA
FLUID AND FILTER (Continued)

(4) Actuate the service brake. Start engine and let
it run at idle speed in selector lever position9P9.
(5) Shift through the transmission modes several
times with the vehicle stationary and the engine
idling
(6) Warm up the transmission, wait at least 2 min-
utes and check the oil level with the engine running.
Push the Oil Dipstick 8863A in up to the stop on the
electrohydraulic unit and pull out again, read off oil
level, repeat if necessary.
NOTE: The dipstick will protrude from the fill tube
approximately 75mm (3 inches) when installed.
(7) Check transmission oil temperature.
NOTE: The true transmission oil temperature can
only be read by a scan tool in REVERSE or any for-
ward gear position. (Refer to 21 - AUTOMATIC
TRANSMISSION- NAG1/TRANSMISSION TEMPERA-
TURE SENSOR/PARK-NEUTRAL SWITCH - OPERA-
TION)(8) The transmission Oil Dipstick 8863A has indi-
cator marks every 10mm. Determine the height of
the oil level on the dipstick and using the height, the
transmission temperature, and the Transmission
Fluid Graph (Fig. 137), determine if the transmission
oil level is correct.
(9) Add or remove oil as necessary and recheck the
oil level.
(10) Once the oil level is correct, install a new dip-
stick tube cap (2) (Fig. 138) and lock pin (1).
STANDARD PROCEDURE - TRANSMISSION
FILL
To avoid overfilling transmission after a fluid
change or overhaul, perform the following procedure:
(1) Verify that the vehicle is parked on a level sur-
face.
(2) Remove locking pin (1) (Fig. 139). Remove the
plate of the locking pin with a suitable tool and press
out the pin remaining in the cap downwards.
(3) Remove cap (2).
(4) Add following initial quantity of Shellt3403 to
transmission:
Fig. 137 NAG1 Transmission Fill Graph
VAAUTOMATIC TRANSMISSION - NAG1 21 - 103
FLUID AND FILTER (Continued)

(a) If only fluid and filter were changed, add5.0
L (10.6 pts.)of transmission fluid to transmission.
(b) If transmission was completely overhauled,
torque converter was replaced or drained, and
cooler was flushed, add7.7 L (16.3 pts.)of trans-
mission fluid to transmission.
(5) Check the transmission fluid (Refer to 21 -
TRANSMISSION/AUTOMATIC - NAG1/FLUID -
STANDARD PROCEDURE) and adjust as required.
STANDARD PROCEDURE - FLUID/FILTER
SERVICE
(1) Run the engine until the transmission oil
reaches operating temperature.
(2) Raise and support vehicle.(3) Remove the torque converter drain plug access
plug from the bottom of the torque converter hous-
ing.
(4) Rotate the engine clockwise until the torque
converter drain plug (Fig. 140) is aligned with the
access hole.
NOTE: Clean the area around the drain plug to pre-
vent dirt from entering the torque converter.
(5) Using a suitable drain pan to catch the fluid,
remove the torque converter drain plug and allow the
torque converter to drain completely.
(6) Inspect the torque converter drain plug seal
(Fig. 140). Replace the seal if necessary.
(7) Install the torque converter drain plug. Tighten
the drain plug to 14 N´m (10 ft.lbs.).
(8) Install the torque converter drain plug access
plug into the bottom of the torque converter housing.
(9) Using a suitable drain pan to catch the fluid,
remove the transmission oil pan drain plug (Fig. 140)
and allow the oil pan to drain completely.
(10) Inspect the transmission oil pan drain plug
seal. Replace the seal if necessary.
(11) Install the transmission oil pan drain plug.
Tighten the drain plug to 20 N´m (15 ft.lbs.).
(12) Remove the bolts and retainers (Fig. 140)
holding the oil pan to the transmission.
(13) Remove the transmission oil pan and gasket
from the transmission.
Fig. 138 Dipstick Tube Cap Components
1 - LOCKING PIN
2 - TUBE CAP
3 - DIPSTICK TUBE
Fig. 139 Remove Dipstick Tube Cap Lock
1 - LOCKING PIN
2 - TUBE CAP
3 - DIPSTICK TUBE
Fig. 140 Fluid/Filter Service Points
1 - OIL FILTER
2 - OIL PAN GASKET
3 - OIL PAN
4 - RETAINER
5 - BOLT
6 - OIL PAN DRAIN PLUG
7 - SEAL
8 - TORQUE CONVERTER DRAIN PLUG
9 - SEAL
21 - 104 AUTOMATIC TRANSMISSION - NAG1VA
FLUID AND FILTER (Continued)

GEARSHIFT CABLE
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE
(1) The floor shifter lever and gate positions
should be in alignment with all transmission PARK,
NEUTRAL, and gear detent positions.
(2) Engine starts must be possible with floor shift
lever in PARK or NEUTRAL gate positions only.
Engine starts must not be possible in any other gear
position.
(3) With floor shift lever handle push-button not
depressed and lever in:
(a) PARK position - Apply forward force on cen-
ter of handle and remove pressure. Engine starts
must be possible.
(b) PARK position - Apply rearward force on cen-
ter of handle and remove pressure. Engine starts
must be possible.
(c) NEUTRAL position - Normal position. Engine
starts must be possible.
(d) NEUTRAL position - Engine running and
brakes applied, apply forward force on center of
shift handle. Transmission shall not be able to shift
from NEUTRAL to REVERSE.
REMOVAL
(1) Move selector lever to position9D9.
(2) Remove top (3) (Fig. 146) of the center section
of instrument panel.
(3) Remove bottom (2) (Fig. 147) of the center sec-
tion of instrument panel.
(4) Pry ball socket of transmission shift cable off
ball knob at the shift lever assembly (SLA). Use a
suitable slotted screwdriver.
(5) Raise and support vehicle.
(6) Detach shift cable at transmission.
(a) Unlatch ball socket latch (Fig. 148) of cable.
(b) Unclip shift cable retainer from retainer
bracket. When pulling out cable, press together
hooks of shift cable retainer at the points shown
(arrows).
(c) Pull shift cable out of ball socket. Ball socket
can remain on transmission lever.
(7) Remove the shift cable grommet from the dash
panel.
(8) Remove the shift cable from the vehicle.
INSTALLATION
(1) Pass the shift cable through the opening in the
dash panel and seat the shift cable grommet into the
hole.
(2) Install the shift cable (Fig. 149) to the trans-
mission.
Fig. 146 Remove Top Section Of Center Instrument
Panel
1 - SHIFT LEVER ASSEMBLY FRAME TRIM
2 - STORAGE COMPARTMENT
3 - TOP CENTER PART OF INSTRUMENT PANEL
4 - SCREW
5 - PLUG CONNECTIONS
6 - ASHTRAY
Fig. 147 Remove Bottom Section Of Center
Instrument Panel
1 - SCREW
2 - BOTTOM CENTER PART OF INSTRUMENT PANEL
VAAUTOMATIC TRANSMISSION - NAG1 21 - 109

INPUT SPEED SENSORS
DESCRIPTION
The input speed sensors (6, 8) (Fig. 165) are fixed
to the shell of the control unit via contact blades. The
speed sensors are pressed against the transmission
housing (2) by a spring (7) which is held against the
valve housing of the shift plate (5). This ensures a
defined distance between the speed sensors and the
exciter ring (4).
OPERATION
Signals from the input speed sensors (6, 8) (Fig.
166) are recorded in the transmission control module
(TCM) together with the wheel and engine speeds
and other information and are processed into an
input signal for electronic control.
Input speed sensor N2 (6) records the speed of the
front sun gear via the externally toothed disc carrier
of the multiple-disc clutch K1 (10) and input speed
sensor N3 (8) records the speed of the front planet
carrier via the internally toothed disc carrier of mul-
tiple-disc clutch K1 (3).
Fig. 162 B2 Piston and Piston Guide Ring
1 - VALVE
2 - PISTON GUIDE RING
3 - B2 PISTON
Fig. 163 Measure B2 Clutch Clearance
1 - PRESSING TOOL 8901
2 - B3 PISTON/B2 OUTER DISC CARRIER
Fig. 164 B2 Clutch Stack-up
1 - B2 OUTER DISC CARRIER
2 - FRICTION DISCS
3 - DISC SPRING
4 - B2 PISTON
5 - OUTER MULTIPLE DISC - 1.8 MM (0.071 IN.)
6 - OUTER MULTIPLE DISC - 1.8 MM (0.071 IN.)
7 - OUTER MULTIPLE DISC - 6.5 MM (0.256 IN.)
8 - SNAP-RING
VAAUTOMATIC TRANSMISSION - NAG1 21 - 119
HOLDING CLUTCH B2 (Continued)

OIL PUMP
DESCRIPTION
The oil pump (Fig. 167) (crescent-type pump) is
installed in the torque converter casing behind the
torque converter and is driven by the drive flange of
the torque converter. The pump creates the oil pres-
sure required for the hydraulic procedures.
OPERATION
When the engine is running, the oil (Fig. 168) is
pumped through the inlet chamber (5) along the
upper and lower side of the crescent to the pressure
chamber (6) of the housing. The meshing of the teeth
prevents oil flowing from the delivery side to the
intake side. An external gear (3), eccentrically
mounted in the pump housing, is located on the
internal gear (4) which is connected to the drive
flange. The crescent (1) drives the external wheel.
DISASSEMBLY
(1) Remove pump gears (1 and 2) (Fig. 169) from
pump housing.
(2) Remove the inner oil pump seal (1) (Fig. 170).
(3) Replace the outer oil pump O-ring (2) (Fig.
170).
Fig. 165 Speed Sensors
1 - DRIVING CLUTCH K1
2 - TRANSMISSION HOUSING
3 - DRIVING CLUTCH K1 INTERNALLY TOOTHED DISC
4 - EXCITER RING
5 - VALVE HOUSING OF SHIFT PLATE
6 - N2 INPUT SPEED SENSOR
7 - SPRING
8 - N3 INPUT SPEED SENSOR
9 - EXCITER RING
10 - DRIVING CLUTCH K1 EXTERNALLY TOOTHED DISC
Fig. 166 Input Speed Sensors
1 - DRIVING CLUTCH K1
2 - TRANSMISSION HOUSING
3 - DRIVING CLUTCH K1 INTERNALLY TOOTHED DISC
4 - EXCITER RING
5 - VALVE HOUSING OF SHIFT PLATE
6 - N2 INPUT SPEED SENSOR
7 - SPRING
8 - N3 INPUT SPEED SENSOR
9 - EXCITER RING
10 - DRIVING CLUTCH K1 EXTERNALLY TOOTHED DISC
Fig. 167 Oil Pump
1 - CRESCENT
2 - OIL PUMP
3 - EXTERNAL GEAR
4 - INTERNAL GEAR
5 - INLET CHAMBER
6 - PRESSURE CHAMBER
21 - 120 AUTOMATIC TRANSMISSION - NAG1VA
INPUT SPEED SENSORS (Continued)