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Section F
65 - 2
Powershift Gearbox
Torque Converter Stall Test, cont'd
Interpreting the Test Results
If all the engine speeds are below the stated figures either
the
engine
is
losing
serviced/overhauled or the torque converter reaction
member clutch is slipping. To check the engine, select
Neutral, open throttle fully and operate an excavator service
to 'blow off' the main relief valve. Engine speed should fall to
slightly below the Maximum Governed Speed (see Engine
Technical Data). If engine speed is correct the torque
converter reaction member clutch is slipping.
If all the engine speeds are higher than the stated figures in
all gears the torque converter safety relief valve may be
faulty. Alternatively there may be internal oil leakage.
If engine speeds are higher than the stated figures in some
gears, check the transmission for clutch slippage or internal
leakage. Look at the example below and see how the results
can be used to isolate a suspect clutch.
Stall Test Results - 6 Speed Powershift
Gear
Clutches engaged
Forward
Rev/min
1st
X,Z
1990
2nd
T,Z
2060
3rd
U,Z
1985
In the example shown, we can see that the engine speed is
abnormally high when 2nd gear forward drive is selected,
indicating a slipping clutch, possibly T or Z. We can now use
the results to determine which clutch is at fault.
From the table we can see that there is no problem with
clutch Z since it is engaged in other gears, the stall speeds
for those gears are normal. This indicates that clutch T is
slipping.
Clutches may be slip for several reasons. Hydraulic leakage
is possible and this can be confirmed by carring out a
pressure test, see Pressure Testing - Individual Clutches.
9803/3280
Transmission
Service Procedures
power
and
should
Reverse
Rev/min
W,Z
1980
V,Z
1975
W,Y
1990
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Section F
65 - 2
Issue 1
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