Land Rover Lt230q Transfer Gearbox Overhaul 2nd Edition Rover Manual

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8
DESCRIPTION AND OPERATION 
						

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DESCRIPTION AND OPERATION9
REAR OUTPUT HOUSING AND TRANSMISSION
BRAKE COMPONENTS
1.Rear output shaft
2.Rear output housing
3.Bolt - rear output housing
4.Speedometer drive gear
5.Spacer
6.Output shaft bearing
7.Circlip
8.Oil seal
9.Mud shield
10.Output shaft flange
11.Felt washer
12.Steel washer13.Self-locking nut
14.Transmission brake backplate
15.Bolt - transmission brake backplate
16.Transmission brake drum
17.Countersunk screw
18.Speedometer driven gear
19.O ring
20.Speedometer driven gear housing
21.Seal
22.O ring *
23.Vehicle speed sensor *
24.Allen screw *
* If fitted 
						

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10
DESCRIPTION AND OPERATION 
						

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DESCRIPTION AND OPERATION11
TRANSFER BOX CROSS SECTION
1.Main casing
2.Front output housing
3.Rear output housing
4.Dog clutch
5.Transmission brake
6.Mainshaft input gear
7.Selective shim - input gear bearing pre-load
8.Intermediate gear cluster
9.Intermediate shaft
10.Collapsible spacer11.Differential assembly
12.Selective shim - differential bearing pre-load
13.Low range gear
14.High/low selector sleeve and hub
15.High range gear and bush
16.Differential rear bearing
17.Front output shaft
18.Differential lock selector shaft
19.Selector fork
20.Rear output shaft
DESCRIPTION
Introduction
The LT230Q transfer box is mounted at the rear of
the main gearbox and transmits drive to the front
and rear axles via the propeller shafts.
The LT230Q, whilst similar to the LT230T differs
mainly in the following areas:
Helix angle of gears increased to 31°together with
an increase in the number of gear teeth thus giving
quieter running and an increase in power
transmission efficiency.
Increased length mainshaft input gears together with
increased thickness bearing housing and
repositioned bearing.
Redesigned intermediate gear bearings.
Redesigned high gear bush giving quieter running.
Construction
The transfer box comprises three main assemblies,
the main casing, front output housing and rear
output housing.
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 output housing carries the front output
shaft and flange, high/low cross shaft, housing and
selector and the differential lock selector shaft and
fork. A dog clutch on the front output shaft is
operated by the differential lock selector fork to
engage/disengage the differential lock.The rear output housing carries the output shaft and
flange and the speedometer drive and driven gears.
A mechanically operated transmission brake is
attached to the housing, the brake drum being
attached to the output flange.
All housings and cover plates are sealed to the main
casing by sealant; mud and water ingress being
prevented by mud shields and throwers located at
each end of the output housings and on the output
flanges.
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. An
additional power take-off gear is located at the rear
of the input gear for certain applications. 
						

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DESCRIPTION AND OPERATION Intermediate gears
The intermediate gear cluster is supported by taper
roller bearings located at each end of the cluster and
running on the intermediate shaft which, in turn, is
supported at the front and rear by the main casing.
Intermediate gear bearing pre-load is achieved by
means of a collapsible spacer positioned between
the bearings, the amount of compression applied to
the spacer is by means of a nut on the end of the
intermediate shaft.
Differential assembly
The differential assembly is supported at the front
and rear by taper roller bearings, the bearing outer
tracks being located in the front and rear output
housings. 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
nut.
The differential assembly comprises front and rear
half carriers with integral shafts and 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 the engagement of the sun gears and load
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.
For certain markets, a neutral warning lamp switch
operated by the high/low selector shaft and an
interlock solenoid are fitted in the main casing.Front output housing assembly
The front output shaft is supported in the front output
housing by a single bearing and is splined into the
differential front shaft.
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.
The differential lock selector housing is also bolted
to the top of the 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. A spring loaded detent ball fitted in
the output housing locates in grooves in the shaft.
A differential lock warning lamp switch operated by
movement of the selector fork and shaft is screwed
into the top of the output housing.
Rear output housing assembly
The rear output shaft is supported in the rear output
housing by a single bearing and is splined into the
differential rear shaft. The output shaft also carries
the speedometer drive gear which meshes with the
driven gear located in the rear output housing.
Lubrication
Lubrication is by splash, oil filler/level and drain
plugs being located in the main casing. An oil
temperature switch is fitted for certain applications. 
						

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DESCRIPTION AND OPERATION13
OPERATION
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 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.
The differential lock, when applied, prevents all
available power being transmitted to the road wheels
offering least resistance and is especially useful for
off-road conditions. When selected, the selector
fork engages the dog clutch on the differential shaft
with a gear on the front output shaft; this locks the
differential and provides fixed drive thereby
transmitting equal power to both output shafts. 
						

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OVERHAUL1
TRANSFER BOX DISMANTLING
1.Clean exterior of transfer box.
2.Drain and discard the oil, refit drain plug.
3.Slacken bolt to release transmission brake
adjustment.
4.Remove countersunk screw securing
transmission brake drum, remove drum.
NOTE: 2 screws may be fitted.
5.Make suitable alignment marks between
transmission brake backplate and rear output
housing.
6.Remove 4 bolts securing transmission brake
backplate, remove backplate.
7.Remove Allen screw securing vehicle speed
sensor - if fitted.
8.Remove vehicle speed sensor, remove and
discard O ring - if fitted.
9.Remove 6 bolts securing bottom cover, remove
cover. 
						

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OVERHAUL
10.Release staking from intermediate shaft nut,
remove and discard nut.
11.Remove bolt securing anti-rotation plate,
remove plate.
12.Using a soft metal drift on threaded end of
intermediate shaft, drive shaft out of main
casing.
13.Remove and discard O ring from intermediate
shaft.
14.Remove and discard O ring from main casing.
15.Wrap a suitable length of wire around
intermediate gears and using assistance, lift
gears out of main casing.
16.Remove and discard 2 taper roller bearings
from intermediate gears.
17.Remove and discard collapsible spacer from
intermediate gears.
CAUTION: Do not remove bearing tracks
at this stage. 
						

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OVERHAUL3
NOTE: Discovery cover plate illustrated.
18.Make suitable alignment marks between cover
plate/power take-off cover, mainshaft input
gear bearing housing and main casing.
19.Noting fitted position of stud nut and
harness/speedometer cable clip, remove 5
bolts and stud nut securing cover plate/ power
take-off cover, recover clip.
20.Remove cover plate/power take-off cover.
21.Remove mainshaft input gear bearing housing.
CAUTION: Do not remove mainshaft input
gear bearing track at this stage.
22.Remove mainshaft input gear together with
taper roller bearings.
NOTE: Input gear fitted to Defender
transfer boxes has an additional dog tooth
gear - see inset on illustration.
23.Remove and discard mainshaft oil seal from
main casing.
CAUTION: Do not remove mainshaft input
gear bearing track at this stage.