Range Rover. Manual - part 144

TRANSFER BOX

DESCRIPTION AND OPERATION

Selector mechanism

The selector mechanism comprises a selector fork
and an interlock spool. The selector fork is mounted
on a shaft between the front and rear casings. The
interlock spool is mounted on a spindle through the
rear casing and is positively connected to the ratio
control motor. The selector fork is engaged in a cam
track on the spool. When the ratio control motor
rotates the spool, the rotational movement of the
spool is converted to linear movement of the selector
along the shaft.

The selector is engaged with the reduction hub. The
linear movement of the selector moves the reduction
hub in the epicyclic gear set changing the ratio
between high, low or neutral.

Lubrication

Lubrication is provided by a low geroter plunger type
oil pump which is driven from the epicyclic gear set.
The oil pump passes oil through oil ways in the
components to lubricate the epicyclic gear set. The
differential unit and morse chain are partially
immersed in oil and are lubricated as the components
rotate.

TRANSFER BOX

NEW RANGE ROVER

DESCRIPTION AND OPERATION

Transfer Box Electrical Components

Ratio control motor

The ratio control motor is located on the rear casing of
the transfer box and secured with four bolts. The
motor comprises a conventional single speed
permanent magnet type motor. The motor spindle has
a worm which engages with a worm wheel in a
housing at the end of the motor. The worm wheel is
attached to the spindle of the selector interlock spool
inside the transfer box.

The worm wheel also drives a motor encoder which
comprises four position switches. The transfer box
ECU provides a 5 V signal to each switch and
interprets the transfer box range by monitoring the
condition of each switch.

The transfer box ECU reads the motor position in the
form of a binary code with each switch either open or
closed circuit. The ECU measures between the
switches and an encoder ground on connector pin 19.

By using the combinations of the switches, the
transfer box ECU can calculate the transfer box
position and how the motor should operate to select
the desired range. If the transfer box should move to a
position outside the normal condition, i.e. left of high
range, the ECU can move the motor to the correct
position.

The table below shows the motor switch states and
the corresponding motor position for each state.

Switch 1

Switch 2

Switch 3

Switch 4

Motor position

Pin 17

Pin 32

Pin 31

Pin 7

Open

Closed

Left stop

Open

Closed

Open

Closed

Left of high

Closed

Open

Closed

High range

Closed

Right of high

Open

Closed

Zone 1

Open

Closed

Open

Neutral

Closed

Open

Zone 2

Closed

Open

Closed

Open

Low range

Closed

Open

Closed

Right stop

Speed sensor

The speed sensor is located in the rear casing and
secured with a screw. A toothed reluctor ring is
integrated on the rear output shaft. The inductive
speed sensor senses the reluctor ring and produces a
sine wave, impulse type signal as each tooth on the
reluctor ring passes the sensor.

The transfer box ECU processes the signal from the
speed sensor and compares this to a stored speed
value in the memory to determine if a range change is
allowed.

NOTE: The speed sensor is dedicated to
the transfer box ECU to determine if a
range change can be permitted.

TRANSFER BOX

DESCRIPTION AND OPERATION

Temperature sensor

The temperature sensor is screwed into the rear
casing. The sensor has two Lucar connectors. One
connector is attached to an earth eyelet connector,
the other is connected to the BeCM.

When the transfer box oil reaches a temperature of
between 140 and 150

C (284 and 302

F), contacts

in the switch close, completing an earth path to the
BeCM. The BeCM uses the completed earth path as a
signal to generate a ’TRANSFER OVRHEAT’
message in the message centre. The ’TRANSFER
OVRHEAT’ message is displayed alternately with a
’REFER HANDBOOK’ message. When the transfer
box oil cools to between 126 and 134

(258 and 273

F), the switch contacts open and the

’TRANSFER OVRHEAT’ message is extinguished.

Transfer box ECU

The transfer box ECU is located below the front LH
seat and is identified from the other ECU’s located
under the seat by its single 36 pin harness connector.
The connector supplies power, earth, signal and
sensor information to/from the ECU and other ECU’s
for transmission operation.

The BeCM, located below the right hand front seat,
contains its own integral fusebox. The transfer box
ECU receives a battery power supply from the BeCM
via fuse number 4. An ignition on signal is also
supplied from the BeCM via fuse 6. The ignition on
signal is supplied to different ECU connector pins for
manual and automatic transmission vehicles.

On NAS only vehicles, if a fault occurs which prevents
the transfer box moving from low to high range, the
transfer box ECU outputs a signal to the ECM which is
interpreted as an OBDII fault flag.

The transfer box ECU provides feed and return paths
to the ratio control motor to operate the motor in the
required direction. Two pins are used to supply power
to the motor in each direction. The feed is supplied
from two pins to avoid overload and heat generation
which would occur if one pin was used. A 5 V signal
current is supplied to the four motor encoder switches
which are used by the ratio control motor to determine
motor position.

Speed signals from the transfer box speed sensor are
received as an input to the transfer box ECU which
calculates whether the speed is below the threshold to
allow a range change.

Range change request signals are received from the
H-gate selector switch on automatic transmission
vehicles or the high/low switch on manual vehicles.

On automatic transmission vehicles, a park/neutral
signal is transmitted from the BeCM to the transfer
box ECU. On manual transmission vehicles, a neutral
switch located in the transmission provides an earth
signal which is used by the ECU and BeCM to
determine that the transmission is in neutral. The
park/neutral and neutral signal are used by the ECU
to allow a range change only when the transmission is
in neutral.

Outputs are provided by the transfer box ECU to the
BeCM for high and low range status. The BeCM uses
the signals for instrument pack message centre
display of range status.

TRANSFER BOX

NEW RANGE ROVER

DESCRIPTION AND OPERATION

Transfer box ECU connector face view

Transfer box ECU connector pin details

Pin No.

Description

Input/Output

Motor drive - Counter clockwise

Output

Motor drive - Counter clockwise

Output

Not used

Ignition - Manual vehicles only

Input

Power earth

Input

Not used

Motor position switch 4

Input

8 to 12

Not used

Vehicle speed signal

Input

Low range status

Output

Transfer box neutral select

Input

Not used

Motor position switch 1

Input

Not used

Motor encoder earth

Output

Not used

Ignition - Automatic vehicles only

Input

Not used

Battery supply

Input

Battery supply

Input

Motor drive - Clockwise

Output

Content .. 142 143 144 145 ..