Mercedes-Benz ML320. Manual — part 191

Fig. 130: Shifting N To D (1st Gear), Function (1st Gear Engaged)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

Fig. 131: Shifting N To D (1st Gear), Function (Engine Started)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

Fig. 132: Shifting N To D (1st Gear), Function (Activation Sequence Active)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Initial Situation:



Selector lever in position "N" or "P".



Engine off.



No pressure in hydraulic system.



All valves in the shift plate in neutral position.

Aim

To engage 1st gear with program "S" selected.

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me

Shifting 2nd gear with program selection "W" or "C" (depending on the production period).

Function

Start engine -

The working pressure (p-A) is formed, reaches via the holding pressure 2-3 shift valve, the command valve 2-3
and ball valve (33a) to the rear multi-disc clutch (K3) and via the command valve 3-4 (31c) to the end face of
the shift pressure 3-4 (29c) shift valve. The 3-4 shift pressure shift valve (29c) is moved against the force of the
spring towards the right. At the same time the 3-4 solenoid valve (Y3/6y4) is energized.

The ECT control unit (N15/3) monitors the engagement process via the reduced speed of the drive shaft as the
frictional connection of the rear multi-disc brake increases. When the speed drops to the specified level, the
ECT control module (N15/3) shuts off the power to the 3-4 shift solenoid valve (Y3/6y4). The spring chamber
of the shift valve B2 (26) is depressurized and switches downward. As a result the line to the opposed surface of
the rear multi-disc brake piston (B2b) is connected to the pressure maintaining valve (32). The pressure on the
opposed surface of the rear multi-disc brake piston (B2b) reduces to a residual pressure.

The 3-4 command valve (31c) moves to the left. The working pressure (p-A) reaches via the holding pressure
shift valve 3-4 (28c) and the command valve 3-4 (31c) to the piston of the rear multi-disc brake (B2a).

The activation sequence is complete; 1st gear is engaged (See Fig. 130.

As a result shift valve pressure (p-SV) reaches the spring chamber of the shift valve B2 (26) and the end face of
the command valve 3-4 (31c).

The shift valve B2 (26) is held in the upper position and the 3-4 command valve (31c) switches towards the
right.

The working pressure (p-a) is replaced by the shift valve pressure (p-SV) at the end face of the shift pressure 3-
4 shift valve (See Fig. 131).

Move Selector Lever From "N" To "D"

The selector lever (52) opens the shift pressure (p-S) feed connection from the ball valve (33b) with the shift
valve B2 (26). In the upper position of the shift valve B2 (26) shift pressure (p-S) reaches behind (p-S) the
piston of the multi-disc brake (B2a) and simultaneously to the opposed surface of the rear multi-disc brake
piston (B2b).

The rear multi-disc brake begins to close. See Fig. 132.

The pressure on the opposed surface of the piston of the rear multi-disc brake (B2b) causes a gentle engagement
of the rear multi-disc brake.

Move Selector Lever From "N" To "R"

The selector valve (52) opens the connection of the feed of shift pressure (p-S) with the center multi-disc brake

2001 Mercedes-Benz ML320

1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662

me