First Gear Engaged - Mercedes-Benz 2005 Sprinter Service Manual

21 - 22 AUTOMATIC TRANSMISSION - NAG1
AUTOMATIC TRANSMISSION - NAG1 (Continued)

First Gear Engaged

The TCM monitors the activation sequence via the
speed of the input shaft, which slows down as the
frictional connection in the multiple-disc holding
clutch increases. When the speed drops to the speci-
fied level, the TCM shuts off the power to the 3-4
shift solenoid valve (10) (Fig. 19). The spring cham-
ber of the shift valve B2 (9) is depressurized and
switches downwards. This connects the line to the
opposing face of the piston B2 (6) with the pressure
holding valve (11). The pressure on the opposing face
of the piston B2 (6) drops to a residual pressure.
The working pressure (p-A) is formed and travels
via the 2-3 holding pressure shift valve, the 2-3 com-
mand valve and the ball valve (16) to multi-plate
clutch K3 (4) and via the 3-4 command valve (13) to
the end face of the 3-4 shift pressure shift valve (14).
The 3-4 shift pressure shift valve (14) is moved
1 - HOLDING CLUTCH B1
2 - DRIVING CLUTCH K1
3 - HOLDING CLUTCH B3
4 - DRIVING CLUTCH K3
5 - HOLDING CLUTCH B2 PISTON
6 - HOLDING CLUTCH B2 PISTON OPPOSING FACE
7 - SHIFT PRESSURE REGULATING SOLENOID
8 - SHIFT PRESSURE REGULATING VALVE
9 - SHIFT VALVE B2
10 - 3-4 SHIFT SOLENOID
against the force of the spring towards the right. At
the same time the 3-4 solenoid valve (10) is ener-
gized. This allows shift valve pressure (p-SV) to enter
the spring chamber of the shift valve B2 (9) and to
reach the end face of the 3-4 command valve (13).
The shift valve B2 (9) is held in the upper position
and the 3-4 command valve (13) switches towards the
right. At the end face of the 3-4 shift pressure shift
valve (14) the working pressure (p-A) is replaced by
shift valve pressure (p-SV).
The 3-4 command valve (13) moves to the left.
Working pressure (p-A) travels via the holding pres-
sure shift valve (12) and the 3-4 command valve (13)
to the piston of multiple-disc holding clutch B2 (5).
Fig. 19 First Gear Engaged
11 - PRESSURE HOLDING VALVE
12 - 3-4 HOLDING PRESSURE SHIFT VALVE
13 - 3-4 COMMAND VALVE
14 - 3-4 SHIFT PRESSURE SHIFT VALVE
15 - 3-4 OVERLAP REGULATING VALVE
16 - BALL VALVE
17 - 1-2/4-5 COMMAND VALVE
18 - 1-2/4-5 COMMAND VALVE
19 - BALL VALVE
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