Hydraulic 2/4 Wheel Drive Unit
(4WD Pressure ON)
Dismantling
Note:
To aid working on this item, use the output yoke as a
stand.
Before dismantling the unit drain the gearbox oil.
1
Hold the yoke
E
using service tool 892/00812 and undo
bolt
F
. Remove the yoke. Carefully remove and discard
oil seal
M
. Be sure not to damage the seal housing.
2
Undo bolts
D
. Lift off the 4WD casing
P
. Lift out the
4WD unit from the gearbox.
3
Remove bearing
1
, only if to be renewed.
4
Remove seal ring
2
. Note, If the piston ring seal is
damaged or excessively worn then check for burrs or
damage on the shaft groove. If necessary remove burrs
with a fine grade abrasion paper and oil.
5
Using a puller remove the 4WD output gear
5
, together
with its bearing
3
, needle roller bearings
6
and thrust
washer
4
. Remove thrust washer
7
. (Note that thrust
washers
4
and
7
are not interchangeable).
6
Remove circlip
8
and shim(s)
9
if fitted. Retain any
shims as a set for assembly.
7
Remove pressure plate
10
, the clutch pack friction
plates
11
and counter plates
12
.
Note:
If only the clutch pack was to be removed, the job is
now complete.
8
Using a suitable press and an adapter similar to
Y
,
compress spring
15
and remove circlip
13
.
9
Remove spring retainer plate
14
, spring
15
and oil baffle
15A
.
10
Withdraw piston
16
then remove and discard 'O' rings
17
and
18
.
Note:
The piston housing cannot be separated from the
shaft, as on the other types of 2/4WD units.
Inspection
Carry out a visual inspection of the friction and counter
plates.
Counter plates - light scoring/polishing is permissible, plates
that are not flat, worn or heavily marked or scored must be
replaced with a new set.
Friction plates - the cross hatching should be clearly visible,
plates that are not flat, have friction material damage or
scoring must be replaced with a new set.
Do not mix old, new and worn plates.
Two different suppliers of the thinner friction plates (1.6 to
1.7 mm, 0.062 to 0.067 in approx) have been used (identify
as brown or green), do not mix the different plates in the
same clutch pack.
Inspect the mating faces of the gearbox and 4WD casings
for damage.
114 - 2
Section F
9803/3280
Section F
114 - 2
Issue 2*
Synchro Shuttle Gearbox
Assembly
If only the clutch pack has been removed, begin at step 4.
1
Grease the shaft, fit new 'O' rings
17
and
18
then locate
piston
16
over the shaft and into the housing.
2
Locate oil baffle
15A
, spring
15
into the piston and
position the retainer plate
14
over the spring.
3
Using a press and adapter
Y
, compress spring
15
and
fit circlip
13
.
4
Build up the clutch pack, installing friction plates
11
and
counter plates
12
alternately, starting with a counter
plate and ending with a friction plate.
5
Install pressure plate
10
, shim(s)
9
and circlip
8
. Using
an air line, blow air down the shaft oil inlet hole and
check the piston and clutch pack is free to operate
smoothly.
6
Measure the clutch pack end float using two
screwdrivers as shown at
B
. End float should be
between 1.0 mm and 2.3 mm. Adjust as necessary, by
adding or removing shims
9
.
7
Fit thrust washer
7
, 4WD gear
5
, needle roller bearings
6
and thrust washer
4
.
8
Press bearing
3
squarely onto the shaft to seat on thrust
washer
4
, taking care not to exert any force on the
housing i.e. rest the unit on the opposite shaft end, not
the housing.
9
Fit new seal
2
.
10
If required, press a new bearing
1
into position, taking
care not to exert any force on the housing (see Step 8).
11
Fit the 2/4WD unit to the gearbox.
12
Apply a thin bead of JCB Multigasket to the 4WD
mating face of the gearbox front case. Fit the case
P
,
apply JCB Threadlocker and Sealer to bolts
D
and
progressively torque tighten to 56 Nm, 46 lbf ft.
13
The 4WD clutch and its associated components are
manufactured using a ‘setright’ system. Provided that
components have been assembled correctly, the shaft
end float will be 0.01 to 0.16 mm (0.0004 to 0.006 in).
Rotate the shaft by hand and ensure that it runs
smoothly. Pull the shaft up and down to detect any
excessive end float. If there is excessive end float or the
shaft runts roughly, dismantle the unit and check for
correct assembly.
14
Fit a new oil seal
M
, fit the output yoke
E
, and flanged
bolt
F
. Torque tighten the bolt to 395 Nm; 291 lbf ft.
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