Land Rover Lt230t Transfer Box Overhaul 3rd Edition Rover Manual

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12
DESCRIPTION AND OPERATION DESCRIPTION
Introduction
The LT230T transfer box is mounted at the rear of
the main gearbox and transmits drive to the front
and rear axles via the propeller shafts.
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 rear 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 the
main casing by gaskets or sealant; mud and water
ingress being prevented by mud shields and
throwers located at each end of the output housings
and on the drive 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.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 compression applied to a spacer
positioned between the bearings. Early transfer
boxes are fitted with a collapsible spacer whilst later
boxes have a selective length, non-collapsible
spacer fitted. 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 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, an interlock solenoid is fitted in
the main casing. 
						

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DESCRIPTION AND OPERATION13
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 front output housing, the selector
finger passes through the housing and locates in a
slot in the differential lock selector shaft. The 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.
For certain markets, a low detect switch, operated
by the high/low selector is screwed into the cross
shaft housing on early boxes or into the side of the
output housing on later boxes.
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 plugs are
located in the main casing. An oil temperature switch
is also fitted for certain applications.OPERATION
The gearbox input 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 a dog clutch on the differential shaft
with a gear on the front output shaft; this locks the
differential and provide fixed drive thereby
transmitting equal power to both output shafts. 
						

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14
DESCRIPTION AND OPERATION Power flow - transfer box in LOW ratio 
						

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DESCRIPTION AND OPERATION15
Power flow - transfer box in HIGH ratio 
						

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OVERHAUL1
TRANSFER BOX DISMANTLING
1.Clean exterior of transfer box.
2.Drain and discard the oil, refit drain plug.
3.Loosen 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.
10.Up to serial no. 288709E:Remove and
discard gasket. 
						

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OVERHAUL
11.Release staking from intermediate shaft nut,
remove and discard nut.
12.Remove bolt securing anti-rotation plate,
remove plate.
13.Using a soft metal drift on threaded end of
intermediate shaft, drive shaft out of main
casing.
14.Remove and discard’O’ring from intermediate
shaft.
15.Remove and discard’O’ring from main casing.
16.Wrap a suitable length of wire around
intermediate gears and using assistance, lift
gears out of main casing.
NOTE: Collapsible spacer illustrated.
17.Remove and discard 2 taper roller bearings
from intermediate gears.
18.Remove and discard spacer from intermediate
gears.
CAUTION: Identify type of spacer fitted i.e.
collapsible or selective length
non-collapsible. Collapsible spacers can
be identified by deformation of the spacer having
occurred during setting of intermediate bearing
pre-load. Collapsible spacers must be replaced
by selective length non-collapsible spacers. Do
not fit collapsible spacers, in place of selective
length spacers. Do not remove bearing tracks at
this stage. 
						

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OVERHAUL3
NOTE: Discovery cover plate illustrated.
19.Make suitable alignment marks between cover
plate/power take-off cover, mainshaft input
gear bearing housing and main casing.
20.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.
21.Remove cover plate/power take-off cover.
22.Up to serial no. 288709E:Remove and discard
gasket.
23.Remove oil feed plate - if fitted, remove and
discard’O’ring.
24.Remove 2 countersunk screws - if fitted
securing mainshaft input gear bearing housing.
25.Up to serial no. 288709E:Remove mainshaft
input gear bearing housing, remove and
discard gasket.
CAUTION: Do not remove mainshaft input
gear bearing track at this stage.
26.From serial no. 288709E:Remove mainshaft
input gear bearing housing.
CAUTION: Do not remove mainshaft input
gear bearing track at this stage. 
						

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OVERHAUL
27.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.
28.Remove and discard mainshaft oil seal from
main casing.
CAUTION: Do not remove mainshaft input
gear bearing track at this stage.
NOTE: Low detect switch fitted to early
boxes illustrated.
29.Remove 6 bolts securing high/low cross shaft
housing.
30.Remove cross shaft housing.
31.Up to serial no. 288709E:Remove and
discard gasket.
CAUTION: Do not carry out further
dismantling of cross shaft housing at this
stage. 
						

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OVERHAUL5
32.Loosen locknut and remove differential lock
warning lamp switch from front output housing.
NOTE: On later boxes, locknut is replaced
by a spacer.
33.Noting fitted position of longest bolt, remove 8
bolts securing front output housing to main
casing.
34.Remove front output housing.
NOTE: Dowel located.35.Up to serial no. 288709E:Remove and
discard gasket.
CAUTION: Do not carry out further
dismantling of front output housing at this
stage.
36.Noting their fitted position, remove shoulder
bolt, 5 bolts and 2 washers securing rear
output housing to main casing.
37.Remove rear output housing.
NOTE: Dowel located.
38.Up to serial no. 288709E:Remove and
discard gasket.
CAUTION: Do not carry out further
dismantling of rear output housing at this
stage.