LT230 Transfer Box - Description and Operation
TRANSFER BOX
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.