66 - 8
Powershift Gearbox
Pressure Testing - Clutches
Isolating a Suspect Clutch
By performing the tests in the first 3 gears in forward and
reverse all the clutches in the gearbox will be engaged,
ensuring any clutch leakage will be easy to identify. Draw a
table as shown so that you can record the results.
1 Stop engine, connect a 0-20 bar (0-300 lbf/in
2
) pressure
gauge to test connector A (mainline pressure test
point).
2 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.
3 Start engine and run at 1000 rev/min, engage 1st gear
forward. Record the pressure reading. Repeat the test
for 2nd and 3rd gears forward and 1st, 2nd and 3rd
gears revers. Record the pressure readings as shown in
the example below:
Readings should not vary between clutches by more than
0.7 bar (10 lbf/in
2
). In the example shown, we can see that
pressure is low when 2nd gear forward is selected,
indicating clutch leakage.
From the table we that the layshaft clutch Z is working
normally (1st and 3rd gear forward and 1st and 2nd gears
reverse all show normal operating pressure). We can
assume that the forward low clutch T is leaking.
By carring out ‘Individual Clutch Leakage Tests', (see next
page) we can confirm that the forward low clutch T is
leaking.
Section F Transmission
9803/3280
Section F
66 - 8
Issue 1
Service Procedures
Clutch Pressure Test Results - 4 Speed Powershift
Gear Clutches engaged
Forward bar lbf/in
2
Reverse bar lbf/in
2
1st T,Z W,Z
2nd U,Z V,Z
3rd T,Y W,Y
Clutch Pressure Test Results - 6 Speed Powershift
Gear Clutches engaged
Forward bar lbf/in
2
Reverse bar lbf/in
2
1st X,Z 13.4 194 W,Z 13.4 194
2nd T,Z 12.0 175 V,Z 13.6 197
3rd U,Z 13.5 195 W,Y 13.5 195
Clutch Pressure Test Results - 6 Speed Powershift
Gear Clutches engaged
Forward bar lbf/in
2
Reverse bar lbf/in
2
1st X,Z W,Z
2nd T,Z V,Z
3rd U,Z W,Y
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