engine MERCEDES-BENZ ML320 1997 Complete Repair Manual

Fig. 106: Torque Converter Lockup Clutch, Function
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Operation
When actuated by the ETC control module (N15/3), oil pressure controlled by the torque converter lockup
PWM solenoid Valve (Y3/6y6) is directed through the input shaft (1) to the pressure chamber behind the piston
(16d). See Fig. 106
. The piston presses the clutch pack (16c) together and allows torque to be transferred
directly between the impeller (P) and turbine wheel (T). The torque converter lockup clutch is activated in 5th,
4th and 3rd gears in relation to the engine speed and engine load.
AUTOMATIC TRANSMISSION, FUNCTION
Transmission without touch shift. 722.6 in MODEL 163, 170, 202, 208, 210.
Transmission 722.6 in MODEL 129, 140.
Automatic transmission 722.6 is an electronically controlled 5-speed transmission with a lockup clutch in the
torque converter.
The ratios for the gear stages are achieved by three planetary gear sets. The 5th gear is designed with a step-up
ratio as an overdrive.
Shifting is initiated electronically. The gears are shifted by the corresponding combination of three
hydraulically actuated multi-plate brakes, three hydraulically actuated multi-disc clutches and two mechanical
freewheels.
Basically automatic transmission 722.6 with electronic control offers the following advantages:
Reduced fuel consumption
Improved shift comfort
More favorable gear steps as a result of 5 gears
Enhanced life and reliability
Reduced servicing costs
The electrohydraulic control unit is bolted onto the bottom of the transmission housing. The end of the
transmission is formed by an oil pan made of sheet steel.
The oil pressure for the converter lockup clutch and center multiple disc clutch is supplied via holes in the input
shaft. The oil pressure to the rear multiple-disc clutch is routed through the output shaft. The lubricating oil is
supplied and distributed by additional bore holes in both shafts. All bearing points of the gear sets as well as
freewheels and shift elements are supplied with lubricating oil.
The parking lock gear and drive flange are connected to the output shaft by gearing.
Freewheels F1 and F2 optimize shiftin
g. The front freewheel (F1) rests against the stator shaft extension on the

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transmission side and connects the sun gear of the front planetary gear set to the transmission housing in the
locking direction.
The torque converter housing and transmission housing are made of a metal alloy. They are bolted together and
centered via the outer multiple-disc carrier of the multiple-disc brake B1. A coated intermediate panel seals the
two components.
The oil pump and outer multiple-disc carrier of the front multiple-disc brake are bolted to the converter housing.
The mechanical part consists of the propeller shaft, output shaft, a sun gear shaft and three planetary gearsets
which are coupled together.
In transmissions for powerful engines, the planetary gearsets have 4 planetary gears, while for less powerful
engines the front and rear planetary gear system has three planetary gear wheels. The stator shaft is pressed into
this and is secured against turning by a spline.
The rear freewheel (F2) connects the sun gear of the center planetary gear set to the sun gear of the rear
planetary gearset in the locking direction.
The electrohydraulic control unit consists of the shift plate made of light alloy for hydraulic control and an
electronic control unit.
The electrical control unit consists of a supporting body made of plastic in which the electrical components are
combined. The shell is screwed to the shift plate. Conductor tracks which are integrated into the shell, connect
the electric components to a plug connector. This 13-pin plug connector forms the connection with the vehicle-
side wiring harness and with the ETC 5 (electronic transmission control) control module (N15/5) via a bayonet
lock.
Automatic Transmission, Location Of Mechanical Components

See AUTOMATIC TRANSMISSION, LOCATION OF MECHANICAL PARTS
.
Automatic Transmission, Location Of Electrical/Electronic Components

See AUTOMATIC TRANSMISSION, LOCATION OF ELECTRIC/ELECTRONIC
COMPONENTS.
Automatic Transmission, Location Of Hydraulic Components

See AUTOMATIC TRANSMISSION, POSITION OF HYDRAULIC COMPONENTS
.
Automatic Transmission, Location of Components, Floor Shift

See AUTOMATIC TRANSMISSION, LOCATION OF COMPONENTS, FLOOR SHIFT
.
Automatic Transmission, Selector Lever Positions


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Automatic Transmission, Driver Information (With Touch Shift)
NOTE: If the shift range is restricted, upshifts occur close to the engine cutoff speed.

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Operation
The term power transmission refers to the transmission of propulsion power and engine torques. Via the
mechanical/hydraulic connection between the engine, torque converter and the downstream automatic
transmission the engine torques are transmitted to the driving wheels and are converted in the transmission via
several planetary gear sets.
Power is transferred in the torque converter via the driven impeller by diverting hydraulic fluid to the turbine
wheel, which is connected to the input shaft. See Fig. 117
.
When the torque converter lockup clutch is engaged, power is transmitted via this mechanical connection. Via
the gear wheels of the individual planetary gear sets the torques coming from the converter are passed on to the
output shaft with the aid of freewheels, multi-disk clutches and brakes, depending on the ratio and shift element
operated.
A reduction of the output speed in the low gears provides lower vehicle speeds with high tractive forces and
drive torques at the drive wheels.
Power Flow In 1st Gear, Function

See POWER FLOW IN 1ST GEAR, FUNCTION
.
Power Flow In 2nd Gear, Function

See POWER FLOW IN 2ND GEAR FUNCTION
.
Power Flow In 3rd Gear, Function

See POWER FLOW IN 3RD GEAR FUNCTION
.
Power Flow In 4th Gear, Function

See POWER FLOW IN 4TH GEAR FUNCTION
.
Power Flow In 5th Gear, Function

See POWER FLOW IN 5TH GEAR FUNCTION
.
Power Flow In Reverse, Function

See POWER FLOW IN REVERSE, FUNCTION
.
Function Of Torque Converter Lock-Up Clutch Control

See FUNCTION OF TORQUE CONVERTER LOCKUP CLUTCH CONTROL
.
Power Flow In 1st Gear, Function

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Center Multi-Disc Clutch (K2)
Center Multi-Disc Brake (B3)
Front Planetary Gear Set
The input shaft (1) drives the internal gear (V4). In drive mode the sun gear (V1) is supported via the locked
freewheel F1 and in overrun mode via the engaged front multi-disc brake (B1) in the housing (B1). The
planetary gears (V2) roll over the fixed sun gear (V1) and provide an increase in torque between the internal
gear (V4) and the planet carrier (V3). The planet carrier (V3) moves at reduced speed in the direction of engine
rotation.
Rear Planetary Gear Set
The internal gear (H4) turns at a reduced speed because of its mechanical connection to the front planet carrier
(H3). The sun gear (H1) is supported via the engaged rear multi-disc brake (B2) and in drive mode via the
locked freewheel (F2), in overrun mode via the engaged rear multi-disc clutch (K3) in the housing. The planet
gears (H2) roll over the fixed sun gear (H1) and provide an increase in torque between the internal gear (H4)
and the planet carrier (H3). The planet carrier (H3) moves at a reduced speed in the direction of engine rotation.
Center Planetary Gear Set
The ring gear (M4) is driven at the same speed as the rear planet carrier (H3) as a result of a mechanical
connection. The sun gear (M1) is supported in the housing via the rear multi-disc brake (B2) (M1). The planet
gears (M2) roll over the fixed sun gear (M1) and provide an increase in torque between the internal gear (M4)
and the planet carrier (M3). The output shaft (5) connected to the planet carrier (M3) turns at a reduced speed in
the running direction of the engine.
Torque Converter, Location/Task/Design/Function

See TORQUE CONVERTER, LOCATION/TASK/DESIGN/FUNCTION
.
Planetary Gear Set, Location/Task/Design/Function

See PLANETARY GEAR SET, LOCATION/TASK/DESIGN/FUNCTION
.
Multiple-Disc Brake, Location/Task/Design/Function

See MULTIPLE
-DISC BRAKE, LOCATION/TASK/DESIGN/FUNCTION.
Multi-Plate Clutch, Location/Task/Design/Function

See MULTI
-PLATE CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.
Location/Task/Design/Function Of Freewheel

See LOCATION/TASK/DESIGN/FUNCTION OF FREEWHEEL
.

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Freewheel (F1)
Center Multi-Disc Clutch (K2)
Front Planetary Gear Set
The planet carrier (V3) and sun gear (V1) are rigidly connected to each other via the engaged front multi-disc
clutch (K1). The planetary gearset is therefore blocked and turns as a closed unit at the input speed due to the
mechanical connection of the ring gear (V4) and propeller shaft.
Rear Planetary Gear Set
The internal gear (H4) turns at the input speed because of its mechanical connection to the front planet carrier
(V3). The sun gear (H1) is supported via the engaged rear multi-disc brake (B2) and in drive mode via the
locked freewheel (F2), in overrun mode via the engaged rear multi-disc clutch (K3) in the housing. The planet
gears (H2) roll over the fixed sun gear (H1) and provide an increase in torque between the internal gear (H4)
and the planet carrier (H3). The planet carrier (H3) moves at a reduced speed in the direction of engine rotation.
Center Planetary Gear Set
The ring gear (M4) is driven at the same speed as the rear planet carrier (H3) as a result of a mechanical
connection. The sun gear (M1) is supported in the housing via the rear multi-disc brake (B2). The planet gears
(M2) roll over the fixed sun gear (M1) and provide an increase in torque between the internal gear (M4) and the
planet carrier (M3). The output shaft (5) connected to the planet carrier (M3) turns at a reduced speed in the
running direction of the engine.
Torque Converter, Location/Task/Design/Function

See TORQUE CONVERTER, LOCATION/TASK/DESIGN/FUNCTION
.
Planetary Gear Set, Location/Task/Design/Function

See PLANETARY GEAR SET, LOCATION/TASK/DESIGN/FUNCTION
.
Multiple-Disc Brake, Location/Task/Design/Function

See MULTIPLE
-DISC BRAKE, LOCATION/TASK/DESIGN/FUNCTION.
Multi-Plate Clutch, Location/Task/Design/Function

See MULTI
-PLATE CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.
Location/Task/Design/Function Of Freewheel

See LOCATION/TASK/DESIGN/FUNCTION OF FREEWHEEL
.
Power Flow In 3rd Gear Function

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Freewheel F1.
Freewheel F2.
Rear multi-disc clutch (K3).
Front Planetary Gear Set
The planet carrier (V3) and sun gear (V1) are rigidly connected to each other via the engaged front multi-disc
clutch (K1). The planetary gearset is therefore blocked and turns as a closed unit at the input speed due to the
mechanical connection of the ring gear (V4) and propeller shaft.
Rear Planetary Gear Set
The center multi-disc clutch (K2) is engaged and transmits the input speed of the input shaft (1) to the planet
carrier (H3) via the hollow gear (M4). The ring gear (H4) turns in the same way as the planet carrier (H3) due to
the mechanical connection with the locked front planetary gearset. This planetary gearset is therefore locked
and turns as a closed unit.
Center Planetary Gear Set
The hollow gear (M4) rotates at input speed due to the engaged center multi-disc clutch (K2). The sun gear
(M1) is supported in the housing via the multi-disc brake (B2). The planet gears (M2) roll over the fixed sun
gear (M1) and provide an increase in torque between the internal gear (M4) and the planet carrier (M3). The
output shaft (5) connected to the planet carrier (M3) turns at a reduced speed in the running direction of the
engine.
Torque Converter, Location/Task/Design/Function

See TORQUE CONVERTER, LOCATION/TASK/DESIGN/FUNCTION
.
Planetary Gear Set, Location/Task/Design/Function

See PLANETARY GEAR SET, LOCATION/TASK/DESIGN/FUNCTION
.
Multiple-Disc Brake, Location/Task/Design/Function

See MULTIPLE
-DISC BRAKE, LOCATION/TASK/DESIGN/FUNCTION.
Multi-Plate Clutch, Location/Task/Design/Function

See MULTI
-PLATE CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.
Power Flow In 4th Gear Function

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Center Multi-Disc Brake (B3)
Freewheel F2
Front Multi-Disc Clutch (K1)
Front Planetary Gear Set
The input shaft (1) drives the internal gear (V4). In the drive mode the sun gear (V1) is supported via the locked
freewheel (f1) and in overrun mode in the housing via the engaged front multi-disc brake (B1). The planet gears
(V2) roll over the fixed sun gear (V1) and provide an increase in torque between the internal gear (V4) and the
planet carrier (V3). The planet carrier (V3) moves at reduced speed in the direction of engine rotation.
Rear Planetary Gear Set
The center multi-disc clutch (K2) is engaged and transmits the input speed of the input shaft (1) to the planet
carrier (H3) via the hollow gear (M4). The internal gear (H4) turns at a reduced speed because of its mechanical
connection to the front planet carrier (V3). The planet gears (H2) turn between the ring gear (H4) and the sun
gear (H1). The sun gear (H1) moves at increased speed in the direction of engine rotation.
Center Planetary Gear Set
The hollow gear (M4) rotates at input speed due to the engaged center multi-disc clutch (K2). The rear multi-
disc clutch (K3) transmits a higher speed to the sun gear (M1) due to the connection to the sun gear (H1). The
planet gears (M2) turn between the ring gear (M4) and the sun gear (M1). The speed of the planet carrier (M3)
and the output shaft connected to the planet carrier (5) lies between that of the ring gear (M4) and the sun gear
(M1). This provides a step-up ratio.
Torque Converter, Location/Task/Design/Function

See TORQUE CONVERTER, LOCATION/TASK/DESIGN/FUNCTION
.
Planetary Gear Set, Location/Task/Design/Function

See PLANETARY GEAR SET, LOCATION/TASK/DESIGN/FUNCTION
. .
Multiple-Disc Brake, Location/Task/Design/Function

See MULTIPLE
-DISC BRAKE, LOCATION/TASK/DESIGN/FUNCTION.
Multi-Plate Clutch, Location/Task/Design/Function

See MULTI
-PLATE CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.
Power Flow In Reverse, Function (Without Touch Shift)

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Torque from the torque converter is increased via the propeller shaft (1) and all three planetary gearsets and
transferred with reversed direction of rotation to the output shaft (5). See Fig. 129
.
The following are not engaged:
Rear Multi-Disk Brake (B2)
Freewheel F2
Front Multi-Disk Clutch (K1)
Front Planetary Gear Set.
The input shaft (1) drive the internal gear (V4). In drive mode the sun gear (V1) is supported via the locked
freewheel (F1) and in overrun mode in the housing via the engaged front multi-disk brake (B1). The planet
gears (V2) roll over the fixed sun gear (V1) and provide an increase in torque between the internal gear (V4)
and the planet carrier (V3). The planet carrier (V3) moves at reduced speed in the direction of engine rotation.
Rear Planetary Gear Set.
The planet carrier (H3) is held securely in the housing due to the engaged center multi-disk brake (B3). The
internal gear (H4) turns at a reduced speed because of its mechanical connection to the front planet carrier (V3).
The planet gears (H2) turn between the ring gear (H4) and the sun gear (H1). The direction is reversed due to
the securely held planet carrier (H3) so that the sun gear (H1) rotates in the opposite direction to the engine.
Center Planetary Gear Set.
The hollow gear (M4) is held securely in the housing by the center multi-disk brake (B3) via the mechanical
connection to the planet carrier (H3). The sun gear (M1) rotates backwards due to the engaged rear multi-disk
clutch (K3). The planet gears (M2) roll over the fixed internal gear (M4) and provide an increase in torque
between the sun gear (M1) and the planet carrier (M3). The output shaft (5) connected to the planet carrier (M3)
turns at a reduced speed in the opposite direction to the running direction of the engine.
Torque Converter, Location/Task/Design/Function

See TORQUE CONVERTER, LOCATION/TASK/DESIGN/FUNCTION
.
Planetary Gear Set, Location/Task/Design/Function

See PLANETARY GEAR SET, LOCATION/TASK/DESIGN/FUNCTION
. .
Multiple-Disc Brake, Location/Task/Design/Function

See MULTIPLE
-DISC BRAKE, LOCATION/TASK/DESIGN/FUNCTION.
Multi-Plate Clutch, Location/Task/Design/Function

See MULTI
-PLATE CLUTCH, LOCATION/TASK/DESIGN/FUNCTION.

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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

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