Page 1393 of 4133

Location/Task/Design/Function Of Freewheel
See LOCATION/TASK/DESIGN/FUNCTION OF FREEWHEEL
.
Function Of Gear Shift (With Touch Shift)
Transmission with touch shift.
On transmission 722.6 the electrohydraulic control unit converts the electric signals going out from the
electronic transmission control (EGS) into hydraulic signals.
Faults occurring in the ETC control unit (N15/3) are handled by the limp-home system. The limp-home system
is designed so that the driver can reach a Service Operation even under extreme conditions.
Selector lever position "P", "R", "N" and "D" are transmitted by the electronic selector lever module control unit
(N15/5) on the Controller Area Network bus class C (engine compartment) (CAN-C) and in parallel to this by
means of a shift rod to the range selector lever at the transmission end. By touching or holding the selector lever
towards "+" or "-" the shift range is pre-selected and displayed in the instrument cluster (A1) until an upshift of
transmission 722.6 is possible.
Function Of Gear Change
See FUNCTION OF GEAR CHANGE
.
Emergency Default Mode, Function
See LIMP
-HOME MODE, FUNCTION.
Function Of Manual Drive Mode Selection
Oil Level Control, Function
See OIL LEVEL CONTROL, FUNCTION
.
Torque Converter Lockup Clutch Control, Function
See FUNCTION OF TORQUE CONVERTER LOCKUP CLUTCH CONTROL
.
Function Of Gear Shift (Without Touch Shift)
On transmission 722.6 the electrohydraulic control unit converts the electric signals going out from the
electronic transmission control (EGS) into hydraulic signals.
Faults occurring in the ETC control unit (N15/3) are handled by the limp-home system. The limp-home system
is designed so that the driver can reach a Service Operation even under extreme conditions.
Selector lever position "P", "R", "N" and "D" are transmitted by the electronic selector lever module control unit
2001 Mercedes-Benz ML320
1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Page 1394 of 4133

(N15/5) on the Controller Area Network bus class C (engine compartment) (CAN-C) and in parallel to this by
means of a shift rod to the range selector lever at the transmission end. By touching or holding the selector lever
towards "+" or "-" the shift range is pre-selected and displayed in the instrument cluster (A1) until an upshift of
transmission 722.6 is possible.
Function Of Gear Change
See FUNCTION OF GEAR CHANGE
.
Emergency Default Mode, Function
See LIMP
-HOME MODE, FUNCTION.
Oil Level Control, Function
See OIL LEVEL CONTROL, FUNCTION
.
Torque Converter Lockup Clutch Control, Function
See FUNCTION OF TORQUE CONVERTER LOCKUP CLUTCH CONTROL
.
Function Of Gear Change
Operation
Every gear change is triggered by the electronic transmission control (ECT). Each shift sequence is assigned a
control block. Each of these contains one overlap regulating valve, one holding pressure shift valve, one shift
pressure shift valve, one common command valve and one electromagnetically actuated switchover valve
(upshift/downshift solenoid valve).
Actuation of the solenoid valve switches over from stationary mode to the shift phase.
When the gear change is complete the solenoid valves are no longer actuated as the different gears are subject to
a self-hold function in stationary mode.
Shifting "N" To "D" (1st Gear), Function
See SHIFTING N TO D (1ST GEAR), FUNCTION
.
Shifting N To D (1st Gear), Function
Transmission 722.6 As Of 1.7.96
2001 Mercedes-Benz ML320
1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Page 1395 of 4133
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
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Saturday, October 02, 2010 3:15:28 PMPage 226 © 2006 Mitchell Repair Information Company, LLC.
Page 1396 of 4133
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
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Saturday, October 02, 2010 3:15:28 PMPage 227 © 2006 Mitchell Repair Information Company, LLC.
Page 1397 of 4133
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 en
gage 1st gear with program "S" selected.
2001 Mercedes-Benz ML320
1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Page 1398 of 4133

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
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Page 1399 of 4133
(B3). The further sequence of the switch-on process is as when engaging the rear multi-disc brake.
Residual Pressure
To avoid air getting into the hydraulic system, which causes a deterioration in shift quality, the line system
remains filled with oil in steady-state operation of the automatic transmission.
Function Of Shift From 1 To 2
See SHIFT FROM 1 TO 2, FUNCTION
.
Shift From 1st To 2nd, Function
NOTE: No mating surface on the piston of the center multi-disc brake (B3).
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1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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Page 1400 of 4133
2001 Mercedes-Benz ML320
1998-03 AUTOMATIC TRANSMISSIONS Complete Transmissions - ML 320 - 722.662
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