L322 Range Rover System Description and Operation
TRANSFER BOX
41-14
DESCRIPTION AND OPERATION
The actuator and gearbox is located on the rear casing and secured with three bolts. The purpose of the actuator and
gearbox is to electrically change the ratio of the transfer box from low to high and visa versa.
The actuator is a DC four brush motor which is controlled by PWM signals from the transfer box ECU. The wires from
the ECU are large diameter and are twisted to minimise electrical interference. The motor has an internal four pin
integral connector which, when installed in the housing, mates with a female connector located in the housing. The
motor housing contains the magnets which, along with the armature and brush assembly, operate the motor. The
housing is located on the armature and brush assembly mounting plate which in turn is secured with screws into the
main housing. The shaft of the armature and brush assembly locates in a pressed plain bearing in the housing and is
adjusted for end float with shims. The opposite end of the shaft has a toothed gear which mates with the reduction
gearbox.
The reduction gearbox comprises an annulus housing, eight planetary gears and a sun gear and carrier plate. The
annulus housing has a shaft and a planet gear carrier plate. The planet gear carrier plate is attached to the shaft inside
the annulus housing. A bevel gear is attached to the opposite end of the shaft on the outside of the housing. The planet
gear carrier plate has four pins which provide the attachment and pivot points for four planet gears. The sun gear and
carrier plate is located in the annulus housing with the sun gear locating between the four planetary gears. The carrier
plate has four pins which provide for the location and pivot points for four further planetary gears. The toothed gear
on the armature and brush assembly shaft locates between these four gears and provides the drive input into the
reduction gearbox.
The housing is manufactured from cast aluminium and is machined to accept the reduction gearbox and the drive
shaft and bevel gear assembly. Three bosses with holes provide for the attachment of the housing to the transfer box
rear casing assembly. An cast aluminium cover is sealed to the housing with two 'O' section gaskets and secured with
six screws. The housing has a machined hole which is fitted with a plain brass bush to accept the drive shaft and bevel
gear assembly. An oil seal is fitted behind the bush to provide a seal between the drive shaft and the transfer box rear
casing half.
A hole in a boss on the housing allows for the fitment of the ten pin electrical connector to the ECU. The connector is
secured in the housing with a spring clip and lip seal. A machined slot in the housing provides location for a second
connector with four female pins. This connector mates with a similar male connector which is an integral part of the
armature and brush assembly mounting plate and supplies power feed and ground connections for the motor.
The drive shaft and bevel gear assembly comprises a machined shaft, bevel gear and a mounting plate. The drive
shaft has internal splines at one end. The splines have a missing tooth to act as a keyway which mates with the lead
screw, providing the correct timing for the lead screw to the motor position. The bevel gear is an interference fit and
is pressed onto the drive shaft. The opposite end of the shaft accepts the mounting plate and has a machined groove
to provide a positive drive for the rotary potentiometer.
The mounting plate is located on the shaft and is secured in the housing with three screws and retains the drive shaft
laterally. An external hexagonal boss on the mounting plate mates with a hexagonal moulding on the potentiometer.
This provides a positive location for the potentiometer, preventing the potentiometer housing from rotating and
providing the correct orientation for the potentiometer connector.
A third connector in the housing has three female pins which mate with similar male pins on the potentiometer. These
pins supply a 5V reference supply, an output signal and ground for the potentiometer. The connector is connected to
the pins of the ten pin electrical connector.
If the actuator and gearbox assembly is to be removed, the synchroniser sleeve position must be set to high range
using TestBook/T4 before the assembly is removed.