E Textbook Power Train & Chassis M2

M-STEP Ver.3

STEP-II
MANUAL TRANSMISSION
& CHASSIS SYSTEM

E BOOK LINK

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MANUAL TRANSMISSION - GENERAL INFORMATION

< CONTENT> PAGES
2
NO ITEMS
1. MANUAL TRANSMISSION TECHNICAL FEATURES 3-4
2. MANUAL TRANSMISSION TECHNICAL SPECIFICATION 5-7
3. MANUAL TRANSMISSION GENERAL CONSTRUCTION
4. 4 WD EASY SELECT TECHNICAL FEATURES 8
5. 4WD EASY SELSECT SYSTEM OPERATION 9 - 20
6. 4 WD SUPER SELECT TECHNICAL FEATURES 20 - 21
7. 4WD SUPER SELECT SYSTEM OPERATION 22 - 31

1 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

TECHNICAL INFORMATION

<R5M21, V5M21>
 Aluminium die-cast undercover of the transmission case has been adopted to improve

case rigidity.
 For 1st and 2nd gears, the double cone synchroniser has been adopted to reduce the

shift operation torque toward them.
 The part-time 4WD is adopted for the 4WD system of the V5M21 transmission. The

easy select 4WD, which can select 2WD/4WD during driving (speed: 100 km/h or less),
has been adopted as option.

<R5MB1, V5MB1>
 The transmission case with tube mechanism has been adopted to improve case rigidity

and reduce noise.
 For 1st and 2nd gears, the triple cone synchroniser has been adopted to reduce the

shift operation torque toward them.
 For 3re gears, the single cone synchroniser has been adopted to reduce the shift oper-

ation torque toward them.
 For the 4WD system of the V5MB1 transmission, the easy select 4WD, which can se-

lect 2WD/4WD during driving (speed:100 km/h or less), has been adopted.

<R6M5A, V6M5A>
 For the manual transmission, newly developed R6M5A and V6M5A has been adopted.
 For 1st, 2nd and 3rd gears, the triple cone synchroniser has been adopted to reduce

the shift operation torque toward them.
 For reverse gear, the synchroniser has been adopted to reduce the shift torque opera-

tion toward the reverse gear.
 There are 2 types of 4WD system; Easy select 4WD and Super select 4WD.

2 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SPECIFICATIONS <Manual transmission>

<2WD>

<4WD>

3 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

CLUTCH SPECIFICATIONS <Manual transmission>

<2WD>
<4WD>

4 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SECTIONAL VIEW <Manual transmission>
<2WD - R5M21>

<2WD - R5MB1>

<R6M5A>

5 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SECTIONAL VIEW <Manual transmission>
<4WD - V5M21>

<4WD - V5MB1>

<V6M5A>

6 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SECTIONAL VIEW <Manual transmission>
<V6M5A> Easy Select 4WD

<V6M5A> Super Select 4WD

7 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

TECHNICAL INFORMATION - Easy Select 4WD

 The easy select 4WD has the following features.
 Transfer mode selection mechanism is operated not only by means of a manual control

(conventional) but also by an electric control.
 The easy select 4WD system, in addition to the 2WD/4WD changeover mechanism.

Thus, 3 drive types of 2WD, direct
 coupling high range 4WD, and direct coupling low range 4WD are selectable, enabling

the 4WD system to cope with any driving conditions.
 The transfer actuator is controlled by a switch which works in conjunction with the drive

mode-selector in order to change the driving mode. This maintains smoother the drive
mode-selector operation and accurate drive mode selection <V6M5A>.
DRIVE METHOD

SYSTEM CONFIGURATION DIAGRAM <V6M5A>

8 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

DESCRIPTION OF CONSTRUCTION AND OPERATION

The operations and functions are the same as these for conventional models.
MAIN STRUCTURAL PARTS

POWER FLOW
The super select 4WD is composed of the 2WD/4WD changeover mechanism, high/low
changeover mechanism and centre
differential as shown in the figure. With operating those, the drive torque transmission meth-
od can be selected.

9 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

High-low switching mechanisms

A helical gear planetary gear, which contributes to a tranquillity, is used in high-low switching
mechanism in order to realise compactness and weight reduction. The input shaft and the
planetary sun gear form one component. The planetary pinion gear is incorporated around
the planetary sun gear. The planetary pinion gear is engaged with the planetary ring gear,
and the pinion shaft of the planetary pinion gear is secured to the planetary carrier.
Centre differential (Torsen® LSD)

A TorsenR LSD is used as the centre differential. Its torque distribution ratio is 40% (for front
axle) and 60% (for rear axle). Then the system redistributes the driving force according to
driving conditions and the driver’s operation to maintain a most suitable ratio. Due to this,
cornering stability has been improved as well as driving stability, which is characteristic of
4WD, is maintained. This unit also contributes to compactness and light weight.
TRANSFER-ECU

The system switches the transfer according to the drive mode-selector and the vehicle con-
ditions. Therefore, the transfer-ECU controls the super select 4WD, the rear differential lock
system (lock/unlock).

10 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

CONTROL UNIT
The transfer-ECU has a hybrid-type 48-pin connector. The terminal layout is as follows.

Fail-safe function
If any of the switches, sensors, transfer actuators and transfer-ECU fails, a fail-safe function
will be activated to protect the passengers and the vehicle.
DIAGNOSIS FUNCTION
The following function have been provided to make inspection of the Super Select 4WD sys-
tem and rear differential lock system easier.
 Diagnosis code output
 Service data output
 Actuator test

11 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

DIAGNOSIS CODES
When diagnosis codes are set, they are stored in the ECU. The diagnosis codes stored in
the ECU (EEPROM) will not be erased even when the battery is OFF. Furthermore, the di-
agnosis codes can be read using the M.U.T.-III.
DIAGNOSIS CODE TABLE

12 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

DIAGNOSIS CODES
When diagnosis codes are set, they are stored in the ECU. The diagnosis codes stored in
the ECU (EEPROM) will not be erased even when the battery is OFF. Furthermore, the di-
agnosis codes can be read using the M.U.T.-III.
DIAGNOSIS CODE TABLE

13 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

14 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA
Using M.U.T.-III, the input data and output data to the transfer ECU can be read.
SERVICE DATA TABLE

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MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA TABLE

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MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA TABLE

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MANUAL TRANSMISSION - GENERAL INFORMATION

ACTUATOR TEST
The actuators can be force-driven by sending signals from the M.U.T.-III to the transfer-ECU.
ACTUATOR TEST TABLE

4WD INDICATOR LAMP
To check the changeover status, the indicator lamps have been provided inside the combi-
nation meter. The lamps illuminate with such a manner that the 2WD, 4WD, and centre dif-
ferential lock status can be discriminated. Also, the lamps flash when the changeover is be-
ing made. The two rear wheel lamps illuminate when 2WD is selected, all the four wheel
lamps illuminate in green when 4WD is selected, and the front heel lamps flash during
changeover. When the centre differential is locked, the centre lamp flashes or illuminates in
amber.

18 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

REAR DIFFERENTIAL LOCK INDICATOR LAMP
The rear differential lock indicator lamp indicates the currently selected mode of operation of
the rear differential lock system. The rear differential lock indicator lamp is located in the
combination meter <Except drive mode selector position 2H and 4H>.

Transfer control
The transfer control is electrically actuated. You can select any mode (2H/4H/4HLc/4LLc) by
rotating the drive mode-selector, which is located on the floor console, when the ignition
witch is turned on. The transfer-ECU controls the transfer actuator according to the electric
signal sent by the drive mode-selector. Then the transfer actuator actuates the mode switch-
ing mechanism in the transfer.

19 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

CONSTRUCTION DIAGRAM

SUPER SELECT 4WD
The super select 4WD has the following features.
 The transfer switching mechanism is electrically actuated.
 The super select 4WD system houses a centre differential in the transfer, in addition to

the High/Low switching mechanism and 2WD/4WD changeover mechanism. Thus, 4
drive types of 2WD, full-time 4WD, direct coupling high range 4WD, and direct coupling
low range 4WD are selectable, enabling the 4WD system to cope with any driving con-
ditions.
 The transfer actuator is controlled by a switch which works in conjunction with the drive
mode-selector in order to change the driving mode. This maintains smoother the drive
mode-selector operation and accurate drive mode selection.
 A torsen® LSD (Limited Slip Differential) has been adopted which distributes the trac-
tion force to the front and rear output shafts in the proportion of 40% to 60%, to main-
tain the driving stability which is a main feature of 4WD driving, and also to improve
steering performance. Furthermore, the adoption of centre differential makes it possible
to distribute the driving force, depending on the road condition.
DRIVE METHOD

20 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SYSTEM CONFIGURATION DIAGRAM

DESCRIPTION OF CONSTRUCTION AND OPERATION
The operations and functions are the same as these for conventional models.
MAIN STRUCTURAL PARTS

21 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

POWER FLOW
The super select 4WD is composed of the 2WD/4WD changeover mechanism, high/low
changeover mechanism and centre differential as shown in the figure. With operating those,
the drive torque transmission method can be selected.

High-low switching mechanisms

A helical gear planetary gear, which contributes to a tranquillity, is used in high-low switching
mechanism in order to realise compactness and weight reduction. The input shaft and the
planetary sun gear form one component. The planetary pinion gear is incorporated around
the planetary sun gear. The planetary pinion gear is engaged with the planetary ring gear,
and the pinion shaft of the planetary pinion gear is secured to the planetary carrier.
Centre differential (Torsen® LSD)

A Torsen R LSD is used as the centre differential. Its torque distribution ratio is 40% (for
front axle) and 60% (for rear axle). Then the system redistributes the driving force according
to driving conditions and the driver’s operation to maintain a most suitable ratio. Due to this,
cornering

22 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

TRANSFER-ECU
The system switches the transfer according to the drive mode-selector and the vehicle con-
ditions. Therefore, the transfer-ECU controls the super select 4WD, the rear differential lock
system (lock/unlock).

CONTROL UNIT
The transfer-ECU has a hybrid-type 48-pin connector. The terminal layout is as follows.

23 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

Fail-safe function
If any of the switches, sensors, transfer actuators and transfer-ECU fails, a fail-safe function
will be activated to protect the passengers and the vehicle.
DIAGNOSIS FUNCTION
The following function have been provided to make inspection of the Super Select 4WD sys-
tem and rear differential lock system easier.
 Diagnosis code output
 Service data output
 Actuator test
DIAGNOSIS CODES
When diagnosis codes are set, they are stored in the ECU. The diagnosis codes stored in
the ECU (EEPROM) will not be erased even when the battery is OFF. Furthermore, the diag-
nosis codes can be read using the M.U.T.-III.
DIAGNOSIS CODE TABLE

24 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

DIAGNOSIS CODE TABLE

25 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

DIAGNOSIS CODE TABLE

26 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA
Using M.U.T.-III, the input data and output data to the transfer ECU can be read.
SERVICE DATA TABLE

27 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA TABLE

28 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

SERVICE DATA TABLE

ACTUATOR TEST
The actuators can be force-driven by sending signals from the M.U.T.-III to the transfer-ECU.
ACTUATOR TEST TABLE

29 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

4WD INDICATOR LAMP
To check the changeover status, the indicator lamps have been provided inside the combi-
nation meter. The lamps illuminate with such a manner that the 2WD, 4WD, and centre dif-
ferential lock status can be discriminated. Also, the lamps flash when the changeover is be-
ing made. The two rear wheel lamps illuminate when 2WD is selected, all the four wheel
lamps illuminate in green when 4WD is selected, and the front wheel lamps flash during
changeover. When the centre differential is locked, the centre lamp flashes or illuminates in
amber.

30 MMMTC VER 1

MANUAL TRANSMISSION - GENERAL INFORMATION

REAR DIFFERENTIAL LOCK INDICATOR LAMP
The rear differential lock indicator lamp indicates the currently selected mode of operation of
the rear differential lock system. The rear differential lock indicator lamp is located in the
combination meter <Except drive mode selector position 2H and 4H>

Transfer control
The transfer control is electrically actuated. You can select any mode (2H/4H/4HLc/4LLc) by
rotating the drive mode-selector, which is located on the floor console, when the ignition
switch is turned on. The transfer-ECU controls the transfer actuator according to the electric
signal sent by the drive mode-selector. Then the transfer actuator actuates the mode
switching mechanism in the transfer.
CONSTRUCTION DIAGRAM

31 MMMTC VER 1

SECTION I

Super Select 4WD System

CONTENTS

1. INTRODUCTION ------------------------------------------------------------- 1-1/ 1-4
(1) Overview of 4WD Systems
(2) 2WD-4WD Switching Mechanism
(3) Differential Unit

2. GENERAL ---------------------------------------------------------------------- 1-5
(1) Specifications
(2) Sectional View

3. FEATURES -------------------------------------------------------------------- 1-6/ 1-8
(1) Drive Methods
(2) System Configuration Diagram
(3) Transfer Control

4. CONSTRUCTION AND OPERATION ---------------------------------- 1-9/ 1-26
(1) Main Structural Parts
(2) Transfer Power Transmission System
(3) Freewheel Mechanism
(4) Rear Differential Lock System
(5) Transfer-ECU

5. INSPECTION & SERVICE PROCEDURES --------------------------- 1-27/ 1-34
(1) Transfer Overhaul
(2) Data List Reference Table
(3) Actuator Test Table

6. KNOWLEDGE CHECK ----------------------------------------------------- 1-35

1. SUPER SELECT 4WD SYSTEM

1. INTRODUCTION

1. Overview of 4WD Systems
In a 4WD system, power is supplied to all four wheels, for better traction on difficult road conditions.
There are two basic types of 4WD system: part-time and full-time.

(1) Part-time 4WD System
In a part-time 4WD system, the driver can shift manually between 2WD and 4WD modes to attain the
best driving performance to suit the road conditions.

<2WD mode>
When the part-time system is in 2WD mode, power is
distributed through the transfer to the rear driveshaft
connected to the rear axle (in a FR layout), but the
driveshaft to the front axle is disconnected, letting the
front wheels turn freely.
2WD mode is quieter and more fuel-efficient than 4WD
mode, and is most suitable for normal driving conditions.

Fig. 1-1

<4WD mode>

When the part-time system is in 4WD mode, power is
distributed through the transfer to both driveshafts,
delivering power to the front and rear axles.
4WD mode provides better traction and pulling power
than 2WD mode, and is most suitable for handling
hazardous road conditions, or when going off-road.

Fig. 1-2

(2) Full-time 4WD System

A full-time 4WD system has the advantage of always being ready for adverse driving conditions,
even when they happen suddenly. For these reasons, full-time 4WD systems have been gaining in
popularity even for passenger cars.

Center differential In a full-time 4WD system, both of front and rear axles
continuously receive power, making the transfer
Rear differential mechanism unnecessary. Since the driver doesn’t
Front differential need to switch between modes, this system offers ex-
cellent safety by handling sudden changes in road
Fig. 1-3 conditions. In a fixed 4WD system, all four wheels are
forced to turn at the same speed, reducing cornering
ability. To overcome this, most 4WD vehicles incorpo-
rate differential systems to distribute torque appropri-
ately, making normal driving in 4WD mode possible.
Power can be distributed directly to the front and rear
axles for a fixed 50:50 torque split, or a center differ-
ential may be used to allow the front and rear axles to
turn at different speeds when cornering (some part-
time systems also use a center differential).

1 - 1 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

2. 2WD - 4WD Switching Mechanism
All part-time 4WD systems use a mechanism to connect and release the front wheels and the pro-
peller shaft. This lets the driver choose the driving mode that best suits driving conditions, selecting
the quiet and efficiency of 2WD, or the traction and control of 4WD.

(1) Front Free-wheel Hubs

<Manual Free-wheel Hubs>
To shift between 2WD and 4WD, it is necessary to lock and unlock the front
wheels from the differential. With manual free-wheel hubs, the driver must exit
the vehicle to lock the hubs.

<Automatic Free-wheel Hubs>
With an automatic free-wheel hub mechanism, shifting from 2WD to 4WD can be
done from inside the vehicle.

Fig. 1-4

(2) Free-wheel Clutch Mechanism

Available exclusively from Mitsubishi on the Easy Se-
lect 4WD and Super Select 4WD systems (SS4/SS4-
II/SS4-i), this mechanism automatically connects and
disconnects the front wheels from the differential for
shifting while driving from 2WD to 4WD and back.

Front synchronized
free-wheel axle

Fig. 1-5

MMMTC VER 1 MAC17 1-2

1. SUPER SELECT 4WD SYSTEM

3. Differential Unit
Though it may not seem like it at first, a car’s wheels are frequently moving at different speeds. As
road conditions change, or just when the car turns, the wheels will speed up or slow down relative to
each other. A differential gear system allows the wheels to move smoothly, even at different speeds.

When cornering, all four wheels travel different distanc-
es. Not only do the outer wheels travel farther than the
inner wheels, the front wheels also travel farther than
the rear wheels.

Red: Front wheels
Blue: Rear wheels

Fig. 1-6

(1) Tight Corner Braking Effect
Because all four wheels are traveling different distances, they are also moving at different speeds.
The braking effect happens when a fixed 4WD system forces all four wheels to turn at the same
speed, which makes steering through tight corners difficult, produces tire noise and causes the ve-
hicle cabin to vibrate and shudder. Tight cornering with a fixed 4WD system can also produce a
potentially damaging effect known as transmission wind-up.

(2) Types of Differential Lock Mechanism
With a basic differential, when one wheel spins freely, the opposite wheel stops turning. To prevent
this, two basic types of differential lock mechanism ensure that wheels with traction receive power.
The first type, such as limited-slip differentials and viscous coupling units, allow smoother driving
control, and only lock for increased traction in slippery conditions. They can only react to poor trac-
tion after it’s encountered, however, so some slipping is inevitable.
The second type, differential locks, keep all four wheels turning the same speed for traction at all
times, but at the price of speed, handling and fuel efficiency.
<Limited-slip Differential>
A limited-slip differential (LSD) is a differential that limits the speed difference between the two
wheels. When one of the wheels loses traction, the LSD distributes torque to the wheel that still has
traction. This helps prevent the car from getting stuck on rough roads.

VCU

(Front, rear and center diff. no LSD) (Front, rear and center diff. with VCU-type LSD)
Wheels turning with trac-
Wheels spinning freely Stopped wheels

In a system with front, rear and center differ- In the same system, but with a center viscous
entials, but no LSD, if both rear wheels lose coupling unit (VCU)-type LSD, the front wheels
traction, the car becomes stuck. still receive torque when the rear wheels slip,

preventing the car from getting stuck.

Fig. 1-7

1 - 3 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

<Differential Lock>
When driving conditions become extremely difficult, a differential lock may be needed to keep from
getting stuck. This system locks all four wheels, making them turn at the same speed regardless of
surface traction. This prevents slipping and will keep the car moving as long as at least one wheel
has traction.

In a system with a differential lock, all four wheels turn
at he same speed for maximum crawling power even
over very difficult terrain.

Rear Differential Lock

Fig. 1-8

MMMTC VER 1 MAC17 1-4

1. SUPER SELECT 4WD SYSTEM

2. GENERAL

The super select 4WD II system which is used for the conventional PAJERO has been adopted for
the transfer drive system.

1. Specifications Item Specification
Super select 4WD II
Drive system High 2speeds, constant mesh
Transfer type Low
Transfer gear ratio Specified lubricants 1
Quantity L 1.9
Transmission oil Specified lubricants Gear oil API classification GL-4 SAE 75W-85
Quantity L 3.2
Transfer oil Gear oil API classification GL-4 SAE 75W-85
2.8

2. Sectional View

10 Transfer input gear Fig. 1-9 21 Front output shaft
11 High/Low clutch 22 Transfer counter gear
12 Low speed gear 16 Chain 23 Reverse idler gear
13 Differential lock hub 17 Viscous coupling unit 24 Counter shaft
14 2WD/4WD synchronizer 18 Centre differential 25 Main shaft
15 Drive sprocket 19 Rear output shaft
20 Transfer drive shaft

1 - 5 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

3. FEATURES
The super select 4WD II has the following features.
◇ The shift actuator is controlled by a switch which works in conjunction with the transfer shift lever

in order to change the driving mode. This maintains smoother lever operation and accurate drive
mode selection.
◇ A planetary gear type centre differential has been adopted which distributes the traction force to
the front and rear output shafts in the proportion of 33% to 67%, to maintain the driving stability
which is a main feature of 4WD driving, and also to improve steering performance. Furthermore,
the adoption of viscous coupling unit (VCU) makes it possible to distribute the driving force, de-
pending on the road condition, between the ratio of 33% to 50% for the front wheel and 67% to
50% for the rear wheel.
◇ The rear differential lock control unit has been integrated with the transfer ECU from ‘09MY PA-
JERO (Up to ‘08MY, the rear differential-ECU was independent). The integrated ECU controls the
transfer changeover and the rear differential lock system. Be noted that the rear differential lock
system is a maker optional equipment.
◇ CAN communication has been adopted for communication with other ECUs in order to decrease
the number of wires and improve information transmission.

1. Drive Methods

Transfer select Drive system High/low Centre differential Road surface conditions
lever position 2WD High Not operating
When driving on general roads and
2H expressways

4H Full-time 4WD High Operating (with viscous When driving on general roads, ex-
4HLc Direct 4WD High coupling unit differential pressways and slippery roads (better
limit) driving stability)

Operating (Lock) When driving on poor roads, sandy
roads and snowy roads

4LLc Direct 4WD Operating (Lock) When greater traction force is re-
Low quired, such as when climbing and
descending steep slopes

C/D LOCK 2H (2WD high range)

Only the rear wheels receive power. This mode is best suited
for highways and normal driving conditions.

C/D LOCK 4H (4WD high range)
C/D LOCK 4WD control with the flexibility of a center differential with
C/D LOCK VCU, gives ready traction on changing conditions or surfaces.
Normally operating with a 33:67 torque split, it can react to
traction loss by automatically redistributing power up to a

4HLc (4WD high range with locked center differential)
With the center differential locked to distribute equal torque to
all four wheels, this mode is suitable for rough back roads or
hazardous weather conditions.

4LLc (4WD low range with locked center differential)
The four-wheel traction of 4HLc shifts into low gear for maxi-
mum torque when going off-road or driving through heavy
snow and mud.

MMMTC VER 1 MAC17 1-6

1. SUPER SELECT 4WD SYSTEM
2. System Configuration Diagram <‘09MY and after>

Fig. 1-10

2WD Free-wheel clutch mechanism 4WD

Hi/Lo switch mechanism VCU E/G T/
E/G T/
MMMTC VER 1 MAC17
Front Differential Rear differential

2WD-4WD Center
transfer differential
mechanism

Fig. 1-11

1-7

1. SUPER SELECT 4WD SYSTEM

3. Transfer Control
The transfer control with the part time 4WD is same as before. A motor-driven select system is used
for transfer control with the super select 4WD II. The operation of this motor-driven select system is
performed by an integrated transfer select lever and switch, which allow the driver to select any one of
four modes (2H, 4H, 4HLc and 4LLc). In addition, the transfer-ECU controls the shift actuators which
drive the drive mode select mechanism inside the transfer based on the electronic signals from the
switch. This system has following features.
◇ Motor-driven drive mode selection allows the selector lever to be operated smoothly and

also ensures accurate mode selection.
◇ The transfer indicator panel has a design which is integrated with the floor console to pro-

vide a feeling of high quality.

Fig. 1-12

MMMTC VER 1 MAC17 1-8

1. SUPER SELECT 4WD SYSTEM

4. CONSTRUCTION AND OPERATION

1. Main Structural Parts

NAME OF STRUCTURAL PARTS OUTLINE OF FUNCTIONS

Solenoid valve A, B Change the negative pressure route acting on the actuators in accordance
with the signals from the transfer-ECU.

A and B turn ON/OFF at the same time.

Freewheel engage switch Detects whether the freewheel mechanism is operating or not operating.

4LLc detection switch Detects the transfer shift range (Low position) from the High/Low shift rail
position.
2WD operation detection switch
Detects the transfer condition (2H position) from the 2WD/4WD shift rail
2WD/4WD detection switch position.

4H detection switch Detects the transfer condition (2H, 4H position) from the main shift rail posi-
tion.
Centre differential lock detection
switch Detects the transfer condition (4H, 4HLc position) from the main shift rail
Front propeller shaft speed sensor position.
Rear propeller shaft speed sensor
Detects the transfer condition (4HLc, 4LLc position) from the main shift rail
position.

Detects the front propeller shaft speed.

Detects the rear propeller shaft speed.

Shift actuator Changes the traction method in accordance with the signal from the trans-
Transfer shift lever switch fer-ECU.

Detects transfer shift lever position.

Rear differential lock switch This automatic restore type switch sends the ON/OFF signal to the rear
differential lock control. A rear differential lock switch is located on the cen-
Rear differential lock detection tre panel.
switch
This switch detects the rear differential state: Locked or Free. It turns ON/
OFF, linked with the move of the differential case drive cam.

Air pump assembly This assembly operates linked with ON/OFF of the rear differential lock
Transfer-ECU switch. However, it can operate only when the vehicle speed is less than 12
km/h.

Sends traction signals to the various mechanisms based on signals from
the various switches and sensors.

Causes the indicator lamps inside the combination meter to flash in order to
indicate the traction condition.

Causes the centre differential lock lamp to flash as a warning to the driver
when there is a problem with the system.

1 - 9 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM
2. Transfer Power Transmission System
The transfer of the super select 4WD II system consists of parts such as a high/low select mecha-
nism, a 2WD/4WD select mechanism, a centre differential, a front output shaft drive section, and a
viscous coupling (VCU) as shown in the illustration below. In the addition, the shift rails are provided
with a detection switch for control purposes.

Center differential
lock detection switch

MMMTC VER 1 MAC17 Fig. 1-13
1 - 10

1. SUPER SELECT 4WD SYSTEM

Fig. 1-14 (1) Power Flow

- When 2H is selected -
When the selector lever is at the 2H position,
the High/Low select mechanism is set to High
and the 2WD/4WD select mechanism is set
to 2WD. The drive power from the transmis-
sion is transmitted directly from the transfer
input gear to the transfer drive shaft. The
drive power is then transmitted to the
2WD/4WD drive section, and because the
differential lock hub and 2WD/4WD hub are
engaged and centre differential does not op-
erate, the drive power is thus transmitted only
to the rear output shaft. At this time, the front
output shaft drive section is free.

Fig. 1-15 - When 4H is selected -
Fig. 1-16 When the selector lever is at the 4H position,
the High/Low select mechanism is set to High
and the 2WD/4WD select mechanism is set to
full-time 4WD. The drive power from the
transmission is transmitted directly from the
transfer input gear to the transfer drive shaft.
Because the 2WD/4WD hub and the drive
sprocket are engaged, the drive power is
transmitted via the centre differential distrib-
utes the drive power to the front and rear out-
put shafts in the ratio of 33% to the front and
67% to the rear. At this time, the centre differ-
ential ensures that smooth driving is provided
even if differences in rotation speed develop
between the front and rear output shafts. In
addition, the centre differential is equipped
with a VCU which acts as a differential limiter,
so that the drive power can be redistributed in
accordance to the difference in rotation speed
so that the optimum per distribution can be
maintained at all times.

- When 4HLc is selected -
When the selector lever is at the 4HLc posi-
tion, the High/Low select mechanism is set to
High and the 2WD/4WD select mechanism is
set to direct 4WD. The drive power from the
transmission is transmitted directly from the
transfer input gear to the transfer drive shaft.
The drive power is then transmitted to the
2WD/4WD select mechanism, and because
the differential lock hub, 2WD/4WD hub and
drive sprocket are engaged, the drive power
is thus transmitted directly to the front and
rear output shafts.

1 - 11 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

Fig. 1-17 When 4LLc is selected -

When the selector lever is at the 4LLc posi-
tion, the High/Low select mechanism is set to
Low and the 2WD/4WD select mechanism is
set to direct 4WD. The drive power from the
transmission is transmitted from the transfer
input gear via the transfer counter shaft to the
transfer drive shaft. The drive power is then
transmitted to the 2WD/4WD select mecha-
nism, and because the 2WD/4WD hub, drive
sprocket and differential lock hub are en-
gaged, the drive power is thus transmitted
directly to the front and rear output shafts.

(2) 2WD/4WD Select Mechanism
The 2WD/4WD select mechanism includes a differential lock function in addition to the High/Low se-
lect function, and it has a total of three selectable positions (2WD, full-time 4WD and direct 4WD).
Furthermore, a synchronizer has been adopted so that 2WD/4WD selection can be carried out while
driving. In addition, a random chain has been adopted as the chain used to drive the front output
shaft, in order to improve quietness of operation.

The 2WD/4WD select mechanism consists of parts such as a differential lock hub, a 2WD/4WD hub,
a drive sprocket, a 2WD/4WD synchronizer sleeve, an outer ring, an inner ring, a synchronizer cone,
and a synchronizer spring as shown in the illustration below. The differential lock hub engages with
the transfer drive shaft the 2WD/4WD hub engages with the sun gear, outer ring and inner ring and
the drive sprocket engages with the synchronizer cone, to rotate as single units. The 2WD/4WD syn-
chronizer sleeve engages with two or three of these units to select the drive method.

Fig. 1-19 Fig. 1-18
MMMTC VER 1 MAC17
- During 2WD (When 2H is selected)
When 2H is selected, the sleeve is positioned as shown
in the illustration at left, and the differential lock hub and
the 2WD/4WD hub are engaged and the drive sprocket is
free. Because of this, the transfer drive shaft and the sun
gear rotate as a single unit, and the centre differential is
locked. In addition, because the drive sprocket is free,
the drive power is transmitted to only the rear output shaft
to drive the rear wheels, and no power is transmitted to
the front output shaft.

1 - 12

Fig. 1-20 1. SUPER SELECT 4WD SYSTEM
Fig. 1-21
During Full-time 4WD (When 4H is selected)
When 4H is selected, the sleeve is positioned as shown
in the illustration at left, and the 2WD/4WD hub and the
drive sprocket are engaged and the differential lock hub
is free. Because of this, the drive power is distributed
from the centre differential to both the sun gear and the
rear output shaft. In addition, because the differential lock
hub is free, the centre differential can freely rotate at dif-
ferential speeds, so that if differences in rotation speeds
should develop between the front and rear output shafts,
these differences can be absorbed to maintain smooth
driving.

During Direct 4WD (When 4HLc/ 4LLc is selected)
When 4HLc or 4LLc is selected, the sleeve is positioned
as shown in the illustration at left, and the differential lock
hub, 2WD/4WD hub and the drive sprocket are all en-
gaged. Because of this, the transfer drive shaft and the
sun gear rotates as a single unit, and the centre differen-
tial is locked and the drive sprocket also rotates. As a re-
sult, the drive power is transmitted evenly to drive both
the front and rear wheels at the same speed.

(3) Double Cone Synchronizer
A double cone synchronizer has been adopted as the
synchronizer in the 2WD/4WD select mechanism. This
synchronizer has the structure shown in the illustration at
left.

Fig. 1-22 The synchronizer spring is ring-shaped, and it sits on top
Fig. 1-23 of the projections (marked with white dot) on the outer
ring and touches the outer ring. On the other hand, pro-
jections are located on the synchronizer spring side of the
synchronizer sleeve splines which match the sections in
between the tabs on the outer ring (marked with black
dot).

1 - 13 MMMTC VER 1 MAC17

Fig. 1-24 1. SUPER SELECT 4WD SYSTEM

Because of this, when the sleeve moves to the side
where the ring is, the centre of the synchronizer spring
which is applied between the ring projections pushes the
projections on the sleeve. As a result, the synchronizer
spring pushes the outer ring, so that a pressing force is
generated on the cone. When the sleeve pushes the syn-
chronizer spring with a large-enough force, the synchro-
nizer spring moves downwards and the sleeve contacts
the chamfered part of the ring. In this way, the synchro-
nizer spring works in the same way as the previous syn-
chronizer gear and spring.

(4) Random Chain
The random chain consists of a combination of alternat-
ing links connected together, and serves to reduce the
amount of noise generated when the chain engages the

Fig. 1-25 (5) Center Differential
Fig. 1-26
MMMTC VER 1 MAC17 The drive force conveyed from the transmission to the
transfer drive shaft is conveyed to the pinion gears of
the centre differential. The drive force from there is con-
veyed to the front output shaft via the sun gear, and
then to the rear output shaft via the annulus gear. The
sun gear and annulus gear are simultaneously driven by
the pinion gear, but as the number of gear teeth differs,
the drive force is distributed to the sun gear (front output
shaft) at a percentage of 33%, and to the annulus gear
(rear output shaft) at 67%. A VCU is mounted between
the sun gear and annulus gear, and the drive force is
changed within a range of 33 to 50% at the front output
shaft and 67 to 50% at the rear output shaft. This ena-
bles travel corresponding to a variety of road surface
conditions, and increases the line traceability during cor-
nering.

Traceability characteristic

Direct Coupled 4WD

SS4 with bevel gear center

Base circle SS4-II with planetary
FF 2WD gear center diff.

Depress accelerator Fig. 1-27

1 - 14

1. SUPER SELECT 4WD SYSTEM

(6) Viscous Coupling Unit
<Construction of V.C.U.>
The construction of the viscous coupling unit adopted with the center differential is as shown below.
The housing is engaged with the annulus gear and the hub is also engaged with the sun gear of the
center differential. Therefore, the housing turns with the rear output shaft and the hub turns with the
front output shaft in 4WD mode.
Within the housing, outer plates (with their outer edge fixed to the housing inside splines) and inner
plates (with their inner edge fixed to the hub outer splines) are arranged alternately.
The outer plates have spacer rings set between them on the outer edge in order to space them, and
are fixed to the housing. In contrast, the inner plates have no such spacer rings, and each can slide
to some extent over the hub spline shaft between the outer plates.
The space between the housing and outer and inner plates is filled with mixture of silicone oil and air.
The viscous coupling is a kind of fluid clutch that uses viscous resistance (shear stress) of the fluid to
transmit power or limit speed differential action. For this purpose, the viscous coupling uses silicone
oil whose viscosity is less variable with temperature changes.

VCU sectional view

Fig. 1-28

Fig. 1-29 <Operation of viscous coupling unit>
- Principle of operation
Refer to the enlarged model consisting of two parallel
plates A and B with fluid filling the space between them
as shown left.
When the plate A moves at velocity V, the fluid that is in
contact with the plate A also moves at velocity V. The
velocity of the fluid decreases gradually in area closer to
the plate B; the area that is in contact with the plate B is
stationary.
Thus there occurs a velocity gradient in the fluid. As the
fluid is viscous, the faster moving fluid molecules devel-
op stronger force (shear stress) to pull or separate, the
slower moving molecules do weaker force (shearing
stress).
This force acts as resistance to the plate A that is mov-
ing at velocity V and as force to the stationary plate to
move it in the same direction as plate A. In other words,

shear stress works to reduce velocity difference of the
two plates.

1 - 15 MMMTC VER 1 MAC17

1. SUPER SELECT 4WD SYSTEM

- Torque Characteristics
When rotation speed different action occurs in the cen-
ter differential, a rotating speed difference occurs be-
tween the inner and outer plates of the viscous coupling,
and the oil between plates is sheared, developing vis-
cous resistance (differential limiting torque). This vis-
cous resistance changes with the rotational speed differ-
ence as shown in the figure left. Namely, the differential
limiting torque increases with rotating speed difference.

Fig. 1-30

<Hump phenomenon>
When continuously applying the rotational speed difference between the case and the hub of the vis-
cous coupling, the temperature of silicone oil increases as time elapsed. And when specific condi-
tions are reached, the internal pressure of the viscous coupling suddenly increases and the differen-
tial limiting torque as well.
When this condition occurs, the forces inside the coupling act in the direction of suppressing the
speed difference until the very high torque condition ends as a result of sufficiently decreased speed
difference. This phase of viscous coupling action is called “hump” phenomenon.
Under the hump phenomenon, the inner plates are shifted close to the outer plates and finally make
metal-to-metal contact with outer plates by the pressure of expanded silicone oil. The torque output
under this condition is not a one transmitted through a shear force of viscous fluid but a one transmit-
ted through friction caused by metal-to-metal contact and is significantly large. The surfaces of inner
and outer plates are given special treatment to protect them from wear that would result from direct
contact between plates during the hump phase of the viscous coupling operation.

Fig. 1-31

MMMTC VER 1 MAC17 1 - 16