DIFFERENTIAL SYSTEM


  1. FUNCTION OF MAIN COMPONENTS

    Models with Rear Differential Lock System
    Component Function
    Differential Lock Shift Actuator Rear Differential Lock Shift Motor Switches the rear differential between free and lock in accordance with signals from the 4WD control ECU.
    Rear Differential Lock Limit Switch Detects the position of the rear differential lock shift motor and transmits a signal to the 4WD control ECU.
    Rear Differential Lock Detection Switch Detects the lock position of the rear differential and transmits a signal to the 4WD control ECU.
    Differential Lock Switch Switches the rear differential between free and lock and transmits a signal to the 4WD control ECU.
    Transfer Shift Actuator Assembly H-L Limit Switch Detects the position of the H-L shift motor and transmits a signal to the 4WD control ECU.
    Center Differential Lock Limit Switch Detects the position of the center differential lock shift motor and transmits a signal to the 4WD control ECU.
    Center Differential Lock Position Switch Detects the lock position of the center differential and transmits a signal to the 4WD control ECU and so on.
    4WD Control ECU Controls the rear differential lock shift motor in response to a signal from each switch.
    Combination Meter Assembly Rear Differential Lock Indicator Light

    • Blinks while the rear differential is being switched between free and lock, and turns on when in lock.

    • Blinks when the switching conditions are not met while the rear differential is being switched between free and lock.
    ABS Warning Light Turns on when ABS and brake assist functions are not operating while the rear differential lock system is switching to lock.
    Multi-information Display* Displays the status of the rear differential lock operation.

    *: Models with Optitron display type combination meter assembly

  2. OPERATING CONDITION


    1. Rear Differential Lock System (Models with BD21BN type rear differential)


      1. The rear differential can only be switched to lock when the drive mode is set to L4L, and when driving at 8 km/h or less. However, the rear differential should not be switched from free to lock while the vehicle is turning or while the wheels are spinning.

      2. The ABS, brake assist and hill-start assist control functions in the brake control system stop while the rear differential lock system is operating. For details, see the Brake Control/Dynamic Control Systems section.

  3. CONSTRUCTION


    1. Differential Lock Shift Actuator and Rear Differential Lock Detection Switch (Models with BD21BN type rear differential)


      1. By rotating the rear differential lock shift motor clockwise or counterclockwise in accordance with a signal from the 4WD control ECU, the rear differential lock shift fork shaft is transferred to switch the rear differential between free and lock.

      2. The rear differential lock limit switch, provided in the differential lock shift actuator, detects the position of the rear differential lock shift motor.

      3. The rear differential lock detection switch, provided on the rear differential carrier sub-assembly, detects that the rear differential lock shift fork is in the lock position.

        B001BQ4E03
        Text in Illustration
        *1 Rear Differential Lock Shift Motor *2 Rear Differential Lock Detection Switch
        *3 Rear Differential Carrier Sub-assembly *4 Rear Differential Lock Limit Switch
        *5 Rear Differential Lock Shift Fork - -
        B001B61E03
        B001BNTE02

    2. Differential Lock Switch (Models with BD21BN type Rear Differential)


      1. Operating the push type rear differential lock switch will switch the rear differential between free and lock.

        B001BUFE05
        Text in Illustration
        *A Models with Multi-terrain Select *B Models without Multi-terrain Select
        *1 Differential Lock Switch - -

    3. TORSEN LSD (Models with BD21BT Rear Differential)


      1. The TORSEN LSD consists of a differential case, 10 planetary gears, 2 side gears, 3 thrust washers and shim. The planetary gears are engaged in pairs, and each pair of planetary gears is engaged with one of the side gears. The planetary gears are supported by the holes provided in the differential case and structured to rotate while revolving around the side gear.

        B001BZ1E01
        Text in Illustration
        *1 Planetary Gear LH *2 Side Gear LH
        *3 Thrust Washer *4 Shim
        *5 Differential Case Cap *6 Planetary Gear RH
        *7 Side Gear RH *8 Screw
        *9 Differential Case Housing - -

      2. The TORSEN LSD conducts differential limiting using friction force generated mainly between the planetary gear and differential case and between the side gear and washer when a velocity difference occurs between the left and right wheels. The friction force is proportional to the differential input torque and is generated by the reaction force between the planetary gear and side gear.

        B001BA6E04

  4. OPERATION


    1. Free-lock Switching of the Rear Differential (Models with BD21BN type Rear Differential)


      1. When the differential lock switch is turned on, the 4WD control ECU outputs drive voltage to the rear differential lock shift motor (M1), and moves the rear differential lock shift fork to the lock side. At this time, the 4WD control ECU uses the rear differential lock limit switch (RLY1, RLY2) to detect the position of the rear differential lock shift motor, and uses the rear differential lock detection switch (RLP) to detect the lock position of the rear differential lock shift fork. When the lock position is reached, the 4WD control ECU stops the output of drive voltage. Also, it causes the rear differential lock indicator light to flash while switching the rear differential between free and lock, and turns on the light after the operation has been completed.

      2. When the differential lock switch is turned off, the 4WD control ECU outputs drive voltage to the rear differential lock shift motor (M2), and moves the rear differential lock shift fork to the free side. When the free position is reached, drive voltage output is stopped and the rear differential lock indicator light is extinguished.

        B001BCFE02
        Text in Illustration
        *1 Rear Differential Lock Limit Switch *2 Rear Differential Lock Shift Motor
        *3 Rear Differential Lock Detection Switch *4 Rear Differential Lock Shift Fork
        *a Free Side *b Lock Side

    2. TORSEN LSD (Models with BD21BT Rear Differential)


      1. The TORSEN LSD responds well to changes in the road surface when driving straight, thus ensuring straight-line stability.

        B001B6HE03

      2. The TORSEN LSD reacts to limit the torque difference between the left and right wheels, thus distributing the coast torque generated by engine braking from the inner wheel to the outer wheel when decelerating during turning. As a result, a yaw moment opposite to the direction of the turn is generated, thus ensuring vehicle stability.

        B001BAHE02
        *1 Coast Torque
        *2 Torque Distribution
        *3 Yaw Moment

      3. The TORSEN LSD reduces drive torque sent to the inner wheel and distributes it to the outer wheel when the inner wheel is slipping during acceleration while turning. As a result, a yaw moment in the turning direction is generated, thus achieving a high level of traction performance and operability.

        B001BVRE02
        *1 Drive Torque
        *2 Torque Distribution
        *3 Yaw Moment

  5. PRECAUTION


    1. TORSEN LSD (Models with BD21BT Rear Differential)


      1. Do not add drive torque with only one of the rear wheels on the ground or with one of the rear wheels spinning. The structure of the TORSEN LSD transmits drive torque to the stopped wheel, which may cause the vehicle to move suddenly without any warning. Also, the differential mechanism may suffer damage in the above situation, possibly leading to a malfunction.

      2. For the left and right rear wheels, equip tires of the same type and size which have roughly similar amounts of wear.