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Powershift Gearbox
Chart A - Machine drives but lacks power in all gears. Gearbox oil may also be overheating.
START
Is gearbox oil level low?
YES
YES
NO
Is gearbox oil the correct type and
YES
free from contamination?
YES
Carry out a Torque Converter Stall Test
in all gears. Are all the stall speeds
YES
outside specifications?
NO
Carry out Mainline Oil Pressure Test
YES
Is mainline oil pressure correct?
NO
Check condition of pressure
maintenance
valve. Clean or renew as applicable.
Check for signs of excessive external
oil leakage.
Carry out Mainline Oil Pressure and
Flow Tests
YES
Is mainline oil pressure /flow correct?
NO
Remove and dismantle gearbox.
Check condition of pump, casings for
internal/external leakage. The clutches
will have been slipping due to low oil
pressure - dismantle all clutches and
renew as required.
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Top up oil level
Check reason for contamination.
Rectify as applicable Drain and flush
oil, see Flushing the Gearbox Oil.
Check the operation of the parking
and service brakes.
NO
Are all the stall speeds too low?
YES
Carry out Torque Converter In
Pressure Test. Is torque converter in
pressure correct?
YES
Carry out Torque Converter Out
Pressure Test. Is torque converter out
pressure correct?
YES
It may be that another fault may have
been overlooked. Go back to the start
of the fault finding and re-check.
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Repair the engine as applicable.
NO
Is the engine performance normal?
See Checking the Engine Power.
Check condition of torque
NO
converter relief valve.
Clean or renew as applicable.
Too high?
Cooler lines restricted or blocked. Oil
YES
NO
Cooler lines or cooler leaking. Internal
Too low?
leakage. Remove the gearbox, torque
YES
converter housing and pump, check
all sealing faces for damage.
Torque converter reaction member
clutch slipping. Remove the gearbox
YES
and renew the torque converter.
cooler blocked.
A396280
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