Mercedes-Benz ML320. Service manual - part 191

 

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Mercedes-Benz ML320. Service 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 

 

 

 

 

 

 

 

 

Content   ..  189  190  191  192   ..