66 - 10
Powershift Gearbox
Pressure Testing - Clutches
Individual Clutch Leakage Test
When testing individual clutch pressures it is necessary to
isolate the clutch being tested. So for instance, on a 6 speed
gearbox, to check the forward low clutch T we must select
2nd gear forward - this would energise the forward low (T)
and layshaft (Z) clutches. Because we only want to check
the forward low (T) clutch pressure and not the layshaft (Z)
clutch pressure, remove the electrical connector to the 6
speed clutch solenoid Zs BEFORE selecting 2nd gear.
Use the table below to determine which solenoid electrical
connectors should be removed when pressure testing
individual clutches. Note that as the first 3 forward and
reverse gears utilise all clutches, there is no need to select
other gears when testing for leakage.
6 Speed Gearbox
Gear Clutches Engaged (Solenoids Energised)
Selected
1st Forward 6 Speed & Layshaft - X,Z (Xs,Zs)
2nd Forward Forward Low & Layshaft - T,Z (Ts,Zs)
3rd Forward Forward High & Layshaft - U,Z (Us,sZ)
1st Reverse Reverse Low & Layshaft - W,Z (Ws,Zs)
2nd Reverse Reverse High & Layshaft - V,Z (Vs,Zs)
3rd Reverse Reverse Low & Mainshaft - W,Y (Ws,Ys)
4 Speed Gearbox
Gear Clutches Engaged (Solenoids Energised)
Selected
1st Forward Forward Low & Layshaft - T,Z (Ts,Zs )
2nd Forward Forward High & Layshaft - U,Z (Us,Zs)
3rd Forward Forward Low & Mainshaf - T,Y (Ts,Ys)
1st Reverse Reverse Low & Layshaft - W,Z (Ws,Zs)
2nd Reverse Reverse High & Layshaft - V,Z (Vs,Zs)
3rd Reverse Reverse Low & Mainshaft - W,Y (Ws,Ys)
In the following procedures the forward low clutch (T) is
tested, therefore in step 2 a pressure gauge is connected to
the forward low clutch test point.
When testing other suspect clutches connect a gauge to the
relevant suspect clutch test point. Because the forward low
clutch is suspect, a gear must be selected that will use the
forward low clutch, in this instance 2nd gear forward.
Note: When testing the 2/4WD clutch remove the feed pipe
R and fit service tool. This pipe incorporates a test point.
Replace the original pipe when testing is complete.
1 Stop engine, connect a 0-20 bar (0-300 lbf/in
2
) pressure
gauge to test connector A, (mainline pressure test
point).
2 Connect a 0-20 bar (0-300 lbf/in
2
) pressure gauge to
test connector T (forward low ratio clutch test point).
3 Remove the layshaft clutch solenoid feed connector Zs,
at the solenoid control valve. This ensures that only the
forward low clutch T is energised when 2nd gear
forward is selected.
4 Make sure that both sides of all four wheels are
chocked. Apply the footbrake and parking brake.
Note: When fully engaged, the parking brake electrically
disconnects the transmission drive; this prevents the
machine from being driven with the parkbrake on. Therefore,
so that we can complete the test, move the parkbrake lever
fractionally forward until the warning light is just
extinguished; hold the lever in this position for the duration
of the test. DO NOT move the lever too far forward,
otherwise the parkbrake will not be fully operational.
Alternatively, disconnect the switch at the park brake.
5 Start engine and run at 1000 rev/min, select 2nd gear
forward. Note the pressure readings on both gauges,
which should not vary by more than 0.7 bar (10 lbf/in
2
).
If the difference on the gauges is greater than 0.7 bar
(10 lbf/in
2
) do the following:
a Stop the engine and interchange the gauges.
b Start the engine and run at 1000 rev/min, select
2nd gear forward. If the difference on the gauges is
still greater than 0.7 bar (10 lbf/in
2
) dismantle the
forward low clutch for servicing.
c If after interchanging the gauges, the readings are
different than at step 5, have the gauges calibrated
and repeat the testing procedure.
Section F
Transmission
9803/3280
Section F
66 - 10
Issue 1
Service Procedures
Ss
Zs
Xs
Ys
Ts
Ws
Vs
Us
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