1999 LAND ROVER DISCOVERY Workshop Manual

TRANSFER BOX - LT230SE
41-12 DESCRIPTION AND OPERATION
Rear output housing components
1Rear output shaft
2Rear output housing
3Bolt - rear output housing
4Spacer
5Output shaft bearing
6Circlip7Oil seal
8Mud shield
9Rear output flange
10Felt washer
11Steel washer
12Self-locking nut

TRANSFER BOX - LT230SE
DESCRIPTION AND OPERATION 41-13
Description
General
The LT 230SE transfer box is mounted at the rear of the gearbox and transmits drive via high or low reduction ratios
to the front and rear axles via the propeller shafts. The high/low ratios are 1.211:1 and 3.32:1 respectively.
Transfer boxes fitted to this model have the prefixes 41D and 42D to the unit serial number. Prefix 41D denotes that
the unit is not fitted with interlock whilst 42D denotes that interlock is fitted.
Vehicles up to 03 model year – Whilst similar to LT230Q transfer boxes fitted to other models, the LT230SE transfer
box has certain engineering modifications incorporated which are as follows:
lUprated torque capacity
lModified front and rear output and cross shaft housings
lIntermediate gear bearing pre-load now controlled by a selective, non-collapsible spacer
lSpeedometer drive and driven gears not fitted for this application
lModified high/low sleeve
lModified front output flange and mud shield
lDifferential lock fitted to certain vehicles, but no longer driver operated
lFixed setting of differential lock warning lamp switch on vehicles fitted with differential lock
Vehicles from 03 model year – The LT230SE transfer box is as described above for vehicles up to 03 model year
with the following modifications:
The following items are introduced on vehicles from 03 model year
lRibs added to main casing to reduce operating noise
lRevised machining process for intermediate gears to reduce operating noise
lBearing retaining nut on the differential carrier has patchlock added to the threads
lInterlock solenoid moved from main casing to selector lever assembly
lIntermediate gears modified with machined internal shoulder and bearing circlips deleted
lDriver operated differential lock
lHigh/Low selector shaft fitted with spring assist
lExisting differential lock switch replaced by 2 new switches of improved design with the additional switch installed
adjacent to the existing switch location.
Construction
The transfer box comprises three main assemblies; the main casing, the front output housing and the rear output
housing. Both output housings and all cover plates are sealed to the main casing by sealant; mud and water ingress
being prevented by mud shields located on the output flanges.
Main casing
The main casing carries the mainshaft input gear, the intermediate gears and the differential, together with the high/
low range gears, selector shaft and fork. The front and rear output housings are bolted to either side of the main
casing.
Transmission neutral sensor
A transmission neutral sensor is fitted on automatic gearbox vehicles for North America and Japan. The sensor is
connected to the BCU and is normally in the open position. The sensor provides an earth path for the BCU which then
interprets the signal and activates an audible warning generated by the IDM if neutral is selected on the transfer box
when the ignition is on.
Transfer box interlock solenoid - Automatic gearbox vehicles
An interlock solenoid is fitted for North America and Japan. The solenoid is located on the top of the transfer box main
casing on vehicles up to 03 model year or on the selector lever assembly on vehicles from 03 model year. The
solenoid is connected to the transfer box relay which, in turn, is controlled by the IDM. The purpose of the solenoid is
to prevent neutral being selected on the transfer box when the ignition key is removed, thereby locking the box in
either high or low ratio.

TRANSFER BOX - LT230SE
41-14 DESCRIPTION AND OPERATION
Mainshaft input gear
The gearbox output shaft is splined into the mainshaft input gear which is supported by taper roller bearings.
Input gear bearing pre-load is achieved by the use of a selective shim located in the bearing housing.
Intermediate gears
The intermediate gear cluster is supported by the taper roller bearings located at each end of the cluster and runs on
the intermediate shaft which, in turn, is supported at the front and rear by the main casing.
A selective spacer, positioned between the gears, pre-loads the intermediate gear bearings when the intermediate
shaft nut is tightened sufficiently to achieve the correct 'torque to turn' of the intermediate gears.
On vehicles from 03 model year, the circlips used to retain the bearings in the intermediate gear are deleted. The bore
of the intermediate gear is machined with a shoulder at each end to locate the bearings.
Differential assembly
The differential assembly is supported at the front and rear by taper roller bearings, the front bearing outer track is
located in the front output housing and the rear bearing outer track is located in the main casing by the rear output
housing. Bearing pre-load is achieved by means of a selective shim located in the front output housing.
The differential rear shaft carries the low range gear, high/low selector sleeve and hub, high range gear and bush and
the differential rear bearing; these components being secured to the shaft by a special staked nut.
The differential assembly comprises front and rear half carriers with integral shafts and with sun and planet gears
mounted on cross shafts within the half carriers. Dished, non-selective thrust washers control the engagement of the
planet gears with the sun gears, whilst selective thrust washers are used to control engagement of the sun gears and
'torque to turn' of the differential. The differential carrier halves are bolted together, a retaining ring providing positive
location of the cross shafts.
The high/low selector shaft and fork are located at the side of the differential, movement of the shaft, fork and selector
sleeve being controlled by the high/low selector finger. A spring loaded detent ball fitted in the main casing, locates
in grooves in the shaft.
On vehicles from 03 model year, the selector fork is modified and fitted with a spring assister and clips to reduce the
effort required to move the selector lever.
Front output housing
The front output housing carries the front output shaft and flange, high/low cross shaft, housing and selector and on
certain vehicles, the differential lock selector shaft and fork.
The front output shaft is supported in the housing by a single bearing and is splined into the differential front sun gear.
High/low selector
The high/low cross shaft is located in a housing bolted to the top of the output housing and is connected to the high/
low selector finger which locates in a slot in the selector shaft.
High/low detect switch
A high/low detect switch is fitted in the front output housing and connects to earth when low is selected. The switch is
connected to the engine ECM, the SLABS ECU and the EAT ECU. The purpose of the switch is to enable selection
of the hill descent feature and to modify the engine fuelling and automatic gearbox gearshift maps stored within the
respective ECM's and ECU's.
Differential lock - If fitted
The differential lock selector housing is bolted to the top of the front output housing, the selector finger passes through
the housing, locating in a slot in the differential lock selector shaft. The differential lock selector shaft passes through
the selector fork which is located beneath a plate bolted to the side of the output housing. The selector fork engages
the dog clutch sleeve with the differential rear shaft when the splines of the sleeve and differential rear shaft are
aligned. A spring loaded detent ball fitted in the output housing locates in grooves in the shaft.

TRANSFER BOX - LT230SE
DESCRIPTION AND OPERATION 41-15
Functionality – Vehicles up to 03 model year only
The function of the differential lock used in previous applications is performed on this vehicle by the Electronic Traction
Control System. However, for the purposes of 2 wheel rolling road testing , the differential lock components are
retained. For all driving conditions however, the differential lock must be set in the unlocked position.
Up to 03 model year specification shown
The differential lock must only be engaged for 2 wheel rolling road testing as engagement of the lock disables the
traction control feature and inhibits correct operation of the electronic brake distribution and hill descent features. It
will also be necessary to disconnect the propeller shaft from the transfer box output shaft driving the axle whose
wheels are NOT on the rolling road. The lock may be engaged/disengaged by using a 10 mm open ended spanner
on the flats (arrowed) machined on the differential lock selector shaft.
Vehicles not fitted with a differential lock may be identified by there being no cover or selector shaft (arrowed) on the
front output housing.
WARNING: VEHICLES NOT FITTED WITH A DIFFERENTIAL LOCK MUST NOT BE TESTED ON A ROLLING
ROAD WHERE THE ROLLERS ARE DRIVEN BY THE VEHICLE.
Functionality – Vehicles from 03 model year only
The differential lock must be engaged for 2 wheel rolling road testing. It will also be necessary to disconnect the
propeller shaft from the transfer box output shaft driving the axle whose wheels are NOT on the rolling road. In
addition, the ETC system must be deactivated by either, removing a fuse (10A fuse 28 in the passenger compartment
fusebox, labelled ABS) or disconnecting the ABS modulator pump. This must be done with the ignition switched off.
Note that the SLABS ECU may record a system fault.
The lock can be engaged or disengaged using the selector lever.
WARNING: VEHICLES NOT FITTED WITH A DIFFERENTIAL LOCK MUST NOT BE TESTED ON A ROLLING
ROAD WHERE THE ROLLERS ARE DRIVEN BY THE VEHICLE.

TRANSFER BOX - LT230SE
41-16 DESCRIPTION AND OPERATION
Differential lock warning lamp switch - if fitted - Vehicles up to 03 model year
A differential lock warning lamp switch connected to the SLABS ECU and operated by movement of the selector fork
and shaft is screwed into the top of the output housing. The switch connects to earth when the differential lock is
engaged.
Differential lock warning lamp switches - Vehicles from 03 model year
Vehicles from 03 model year are fitted with two differential lock warning lamp switches.
Both switches are of a new design and are fitted into the top of the front output housing. The switches are connected
to the SLABS ECU and are operated by movement of the selector shaft.
Both switches have an aluminium washer which seals the switch to the casing and also sets the switch position,
removing the requirement for a setting procedure.
Both switches are connected in parallel to earth when the differential lock is engaged. This earth is sensed by the
SLABS ECU which illuminates the differential lock warning lamp in the instrument pack.
Differential lock warning lamp - Vehicles up to 03 model year – if fitted
The differential lock warning lamp is located in the instrument pack and provides a warning to the driver when the
ignition is switched on that the differential lock is engaged. The warning lamp illuminates in a Red colour.
With the lock engaged, the traction control and electronic brake distribution warning lamps will also be illuminated.
Disengagement of the differential lock should be carried out with the ignition switched off. The warning lamps must
be extinguished when the ignition is switched on again.
Differential lock warning lamp – vehicles from 03 model year
The differential lock warning lamp is amber coloured and is located in the instrument pack.
When the lock is engaged, the warning lamp is illuminated and the instrument pack sounder emits three audible
chimes. When the lock is disengaged, the warning lamp is extinguished and the instrument pack sounder emits three
audible chimes.
Rear output housing
The rear output housing carries the output shaft and flange. A cable operated transmission brake is attached to the
housing, the brake drum being attached to the output flange.
The rear output shaft is supported in the housing by a single bearing and is splined into the differential rear sun gear.
Lubrication
Lubrication is by splash, oil filler/level and drain plugs being located in the main casing.
Internal pressures caused by thermal expansion and contraction are avoided by the use of a plastic breather pipe
venting the interior of the box to atmosphere. The pipe is attached to the top of the high/low selector housing by a
banjo bolt and is then routed in a continuously rising path into the engine compartment where the open end is secured
by a clip attached to the engine cylinder block.
Oil temperature warning lamp switch
An oil temperature switch is fitted to V8 engine models up to 03 Model Year. In the event of the transfer box oil
approaching maximum recommended working temperature of 145°C (293°F), the switch will close and a warning
lamp in the instrument pack will be illuminated.

TRANSFER BOX - LT230SE
DESCRIPTION AND OPERATION 41-17
High/Low range and differential lock selector lever assembly – Vehicles from 03 model year
1Selector lever
2High/Low range cable
3Differential lock cable4Interlock solenoid - North America and Japan
only
On vehicles fitted with a differential lock, the high/low range selector lever as fitted on previous models also
incorporates the differential lock selector on vehicles from 03 model year.
The lever can be moved forwards or backwards to select high, neutral or low range or sideways to select differential
lock engaged or disengaged, on vehicles with differential lock fitted.
The selector lever assembly comprises an aluminium casting with bosses for location of the two cables, the selector
lever mechanism and a housing for the interlock solenoid (if fitted). The upper face of the casting has threaded holes
which allow for the attachment of the casting to the mounting plate which is attached to the transmission tunnel.
A boss at the front provides location for the differential lock cable. The cable is attached to a lever which in turn is
attached to the selector lever. Movement of the selector lever is passed via the lever to the cable which moves the
differential lock selector shaft.
A second boss provides for the location of the high/low range cable. The cable is attached to a plate which moves in
a forward or rearward direction with the selector lever. On North American and Japanese specification models, plate
movement is prevented by an interlock solenoid when the ignition key is not in the ignition.
When fitted, the interlock solenoid is located on the right hand side of the selector lever casting. The solenoid is fitted
into a cast housing in the casting and retained with a circlip. Sealant is applied over the circlip to seal the solenoid in
the housing to prevent the ingress of dirt and moisture. The solenoid performs the same function as on previous
models, preventing the selection of neutral on the transfer box when the ignition key is not in the ignition.
A setting procedure is required for both the differential lock cable and the high/low range cable.

TRANSFER BOX - LT230SE
41-18 DESCRIPTION AND OPERATION
Operation
Power flow - transfer box in LOW ratio
Up to 03 Model Year section shown. from 03 Model Year similar

TRANSFER BOX - LT230SE
DESCRIPTION AND OPERATION 41-19
Power flow - transfer box in HIGH ratio
Up to 03 Model Year section shown, from 03MY similar
The gearbox output shaft transmits power to the mainshaft input gear which is in constant mesh with one of the
intermediate gears. The intermediate gears are in constant mesh with the high and low range output gears running
on the differential rear shaft.
Power is transmitted to the output shafts via the differential assembly by locking either the high or low range gears to
the differential rear shaft. This is achieved by means of the high/low selector fork, sleeve and splined hub.