transmission LAND ROVER DISCOVERY 1999 Owner's Manual

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
41-16 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
41-24 REPAIRS
Cable - selector - differential lock
$% 41.20.12
Remove
1.Remove centre console.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Console - centre - automatic
models.
2.Remove 4 bolts securing transfer gearbox high/
low selector lever to transmission tunnel.
3.Remove front propeller shaft.

+ PROPELLER SHAFTS, REPAIRS,
Propeller shaft - front.
4. Models fitted with high/low shift interlock
solenoid: Release interlock solenoid multiplug
and disconnect multiplug from main harness.
5. Models fitted with high/low shift interlock
solenoid: Remove sleeve retaining rings and
remove sleeve from high/low select cable.
6.Release and remove clevis pin and 'C' clip
securing transfer gearbox high/low selector
cable to transfer gearbox high/low selector
lever. Position the cable aside.7.Release and remove clevis pin securing
differential lock selector cable to transfer
gearbox.
8.Loosen locknuts securing differential lock
selector cable to differential lock selector cable
abutment bracket.
9.Release and remove differential lock selector
cable from differential lock selector cable
abutment bracket.
10.Remove transfer gearbox high/low selector
lever assembly from transmission tunnel.
11.Release and remove clevis pin and 'C' clip
securing differential lock selector cable to
differential lock selector lever. Remove the
differential lock selector cable.

TRANSFER BOX - LT230SE
REPAIRS 41-25
Refit
1.Fit differential lock selector cable to differential
lock selector lever and secure with clevis pin
and 'C' clip.
2.Position transfer gearbox high/low selector
lever assembly to transmission tunnel.
3.Position differential lock selector cable to
differential lock selector cable abutment
bracket and tighten locknuts sufficiently to
retain cable.
4.Fit differential lock selector cable to transfer
gearbox and secure with clevis pin.
5.Fit transfer gearbox high/low selector cable to
transfer gearbox high/low selector lever and
secure with clevis pin and 'C' clip.
6.Fit transfer gearbox high/low selector lever to
transmission tunnel, fit bolts and tighten to 10
Nm (7 lbf.ft).
7. Models fitted with high/low shift interlock
solenoid: Position interlock solenoid harness
to high/low shift cable, fit sleeve around cable
and harness and secure sleeve.
8. Models fitted with high/low shift interlock
solenoid: Connect solenoid multiplug to main
harness and secure multiplug to bracket.
9.Check and adjust differential lock selector
cable.

+ TRANSFER BOX - LT230SE,
ADJUSTMENTS, Cable - selector -
differential lock - adjust.
10.Fit centre console.

+ INTERIOR TRIM COMPONENTS,
REPAIRS, Console - centre - automatic
models.
Transfer box - Diesel
$% 41.20.25.99
Remove
1.Remove front exhaust pipe.

+ MANIFOLDS AND EXHAUST
SYSTEMS - Td5, REPAIRS, Pipe - front.
2.Raise vehicle on ramp.
3.Drain transfer box oil.

+ MAINTENANCE, PROCEDURES,
Transfer box.
4.Remove 3 nuts securing intermediate silencer
to tail pipe.
5.Release silencer from mounting rubbers.
6.Remove silencer and discard gasket.
7.Remove front propeller shaft.

+ PROPELLER SHAFTS, REPAIRS,
Propeller shaft - front.
8.Remove rear propeller shaft.

+ PROPELLER SHAFTS, REPAIRS,
Propeller shaft - rear.

TRANSFER BOX - LT230SE
OVERHAUL 41-55
Reassembly
1.Lubricate all components with recommended
oil and lightly oil the differential bolt threads.
2.Secure rear half of differential carrier in a soft
jawed vice.
3.Fit each planet gear to its respective cross
shaft, fit new dished thrust washer to each
gear.
4.Fit cross shafts, planet gears and dished thrust
washers in rear half of carrier.Ensure that
cross shafts are fitted correctly. Do not fit
the sun gear into the rear half carrier at this
stage.
5.Fit retaining ring.
6.Fit a 1.05 mm (0.04 in) thrust washer to sun
gear from front half of carrier. Position gear in
front half of carrier.
7.Ensuring that assembly marks are aligned, fit
both halves of carrier together.
8.Fit the differential carrier bolts and, working in a
diagonal sequence, tighten the bolts to 60 Nm,
(44 lbf.ft).9.Insert the front output shaft into the front half of
the carrier and check that the gears rotate
freely.
10.Fit output flange on to the splines of the output
shaft, but do not fit flange nut at this stage.
11.Fit transmission brake drum to output flange
and secure the drum using 2 nuts.
12.Secure a length of cord around the drum and
attach one end of the cord to a spring balance.
13.Pull on the spring balance and note the load at
which the brake drum starts to turn. Used
gears should rotate smoothly, while new
gears will have a 'notchy' feel as they rotate.
14.Compare the figure obtained with the following.
lUsed gears = 0.45 kg (1.0 lb)
lNew gears = 1.72 kg (3.8 lb)
15.If the load to turn figure is below the specified
limits, proceed as follows.
16.Remove the front output shaft and brake drum.
17.Remove the 8 bolts securing the two halves of
the differential carrier
18.Separate the differential carrier and remove the
sun gear and thrust washer from the front half.
19.Select a thicker thrust washer from the range
available. 5 different thrust washers are
available, rising in increments of 0.10 mm
(0.004 in) from 1.05 mm to 1.45 mm (0.04 to
0.06 in).
20.Repeat steps 7 to 19 as necessary until the
load to turn figure is as specified
21.When specified load to turn is obtained,
proceed as follows.
22.Remove the front output shaft and brake drum.
23.Remove the 8 bolts securing the two halves of
the differential carrier
24.Separate the differential carrier and remove the
sun gear and thrust washer from the front
half.Retain the selected thrust washer with
its sun gear.

TRANSFER BOX - LT230SE
41-56 OVERHAUL
25.Remove retaining ring, then remove the planet
gears and cross shafts.
26.Fit a 1.05 mm (0.04 in) thrust washer to sun
gear from rear half of carrier. Position gear in
rear half of carrier.
27.Fit planet gears, cross shafts and dished thrust
washers to rear half of carrier. Ensure that
cross shafts are fitted correctly. Do not fit
the sun gear into the rear half carrier at this
stage.
28.Fit retaining ring.
29.Ensuring that assembly marks are aligned, fit
both halves of carrier together.
30.Fit the differential carrier bolts and, working in a
diagonal sequence, tighten the bolts to 60 Nm,
(44 lbf.ft).31.Invert the assembly in the vice, insert the rear
output shaft into the rear half of the carrier and
check that the gears rotate freely.
32.Fit output flange on to the splines of the output
shaft, but do not fit flange nut at this stage.
33.Fit transmission brake drum to output flange
and secure the drum using 2 nuts.
34.Carry out the load to turn check, using the same
method as for the front half carrier. Record the
shim thickness when the load to turn is correct.
35.Fit the sun gear and selected thickness shim to
the front half carrier.
36.Ensuring that assembly marks are aligned, fit
both halves of carrier together.
37.Fit the differential carrier bolts and, working in a
diagonal sequence, tighten the bolts to 60 Nm,
(44 lbf.ft).
38.With differential assembled, fit rear output shaft
and brake drum, then check overall load to turn.
This should be approximately the same as the
combined load to turn figure of both front and
rear half carriers.
lUsed gears = 0.90 kg (2.0 lb)
lNew gears = 3.44 kg (7.6 lb)

AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION 44-1
AUTOMATIC GE ARBOX - ZF4HP22 - 24 DESCRIPTION AND OPERAT ION
Automatic gearbox component layout
1Selector lever assembly
2Gearbox
3Electronic automatic transmission ECU
4Selector position switch5Oil cooler
6Fluid lines
7Breather tube
8Selector cable

AUTOMATIC GEARBOX - ZF4HP22 - 24
DESCRIPTION AND OPERATION 44-3
1Transmission high/low switch
2Mode switch
3Gear position switch connector
4Solenoid valve/speed sensor connector
5Electronic automatic transmission ECU
6Engine control module
7Diagnostic socket
8Instrument pack
9Transmission fluid temperature sensor
10Body control unit
11Battery power supply
12Ignition power supply

AUTOMATIC GEARBOX - ZF4HP22 - 24
44-4 DESCRIPTION AND OPERATION
Description
General
The automatic gearbox is a four speed unit with electronic control of gear selection, shift quality and torque converter
lock-up. Selections on the selector lever assembly are transmitted to the gearbox by a selector cable. A gear position
switch on the gearbox transmits the gear selection to an Electronic Automatic Transmission (EAT) ECU, which
outputs the appropriate control signals to an electro-hydraulic valve block in the gearbox. A mode switch enables the
driver to change the control mode of the EAT ECU. The EAT ECU operates warning lamps in the instrument pack to
indicate the control mode and system status.
The gearbox features a pressure lubrication system and is cooled by pumping the lubricant through an oil cooler.
On NAS market vehicles from 03 model year, the ZF 4HP24 transmission unit is introduced for use with the 4.6 litre
V8 engine. This transmission is required to accomodate the increased power output of the larger engine. The ZF
4HP22 transmission remains in use on vehicles with Td5 and 4.0 litre V8 engines.
Both transmission units are of similar construction, with the ZF 4HP24 unit being 15 mm longer than the 4HP22 unit
to accomodate a larger fluid pump. The operation of both transmission units is the same.