300Tdi Defender Transfer Gearbox Upgrade
TRANSFER GEARBOX
1
DESCRIPTION AND OPERATION
TRANSFER GEARBOX
Description
The transfer gearbox is a permanent 4 wheel drive,
two speed ratio reducing gearbox, incorporating high
and low range outputs with mechanically lockable
centre differential (diff-lock). High/low range and
diff-lock selection are made via a single lever located
forward of the main gear lever.
The transfer gearbox is mounted at the rear of the
main gearbox, the mainshaft of which extends into the
transfer casing. A transfer gear, supported on taper
roller bearings and splined to the gearbox mainshaft,
passes the drive to an intermediate gear cluster
supported on a single shaft and rotating on taper roller
bearings.
The intermediate gears pass the drive to high and low
speed gears on the rear output shaft. The rear output
shaft passes through the speedo drive housing, which
also forms the mounting for the transmission brake. A
worm gear fitted to the rear output shaft drives a
pinion fitted in the speedo housing.
Integral with the output shafts is a differential
assembly which compensates for speed differences
between the front and rear prop shafts. To prevent all
the power being transmitted to the axle offering the
least resistance, a diff-lock is provided. The differential
lock should only be engaged during severe off-road
conditions and should be disengaged as soon as
conditions permit. Selection of differential lock
engages, through mechanical linkage, a dog clutch
with the front output shaft, this action locks the centre
differential and provides a fixed drive, giving equal
power to the front and rear output shafts.
