14 - 4
Checking Wheel Speed
The pump output and general efficiency of the drive system
may be checked by raising the machine off the ground and
checking the wheel speeds using a stroboscopic meter.
!!
WARNING
The following procedure requires the machine to be
disabled (wheels raised off the ground, work function
disconnected etc.) while the work is carried out.
HYD 8-1/1
Place the machine safely onto blocks, so that all four wheels
are clear of the ground. Ensure that the machine is stable.
Stick a piece of reflective tape on a wheel rim. Start the
engine and run at maximum speed then operate the drive
control. Measure the speed of wheel rotation in each direction
which should be 81 rev/min. An allowance of 2% above this
figure is permissible. Check the speed of the wheels on the
opposite side of the machine.
Note that excessive wheel speed may result in cooling
problems due to overheating of the hydraulic oil.
Adjustment - Servo Machines
If necessary the appropriate adjusting screws should be
screwed in 4 turn at a time until the correct wheel speed is
achieved. Stop the engine while adjustment is carried out.
1 Remove the seat and floorplate to expose the pump.
Note: Diagram X shows servo pump up to machine no.
676354. Illustration Y shows servo pump from machine no.
676355.
2 If the left hand wheels are rotating too fast in forward or
reverse, screw in adjusters B (forward) or D (reverse) to
achieve the correct speed. If the right hand wheels are
rotating too fast, screw in adjusters A (forward) or C
(reverse).
If all four wheels rotate slowly and cannot be corrected by
adjustment, the most likely cause would be internal wear of
the hydrostatic pump.
If the wheel speed is slow on one side only, the cause could
be a faulty servo or a faulty motor. Carry out procedure on
page E14-3 to determine which is faulty.
Following this procedure, further small adjustments may be
required to achieve correct straight line travel (see pages
E14-5 and E14-6).
Section E
Hydraulics
9803/8500
Section E
14 - 4
Issue 1
Problem Solving
The diagram above shows the servo units when viewed from
the side door of the cab.
Adjustment - Manual Machines
If the correct wheel speed cannot be achieved, check that the
control linkage is correctly adjusted and giving maximum
pump swash.
To adjust for correct straight line travel on manual machines,
refer to page E14-7.
If maximum pump swash is achieved and the wheel speed is
not correct, the pump or motor could be faulty. Carry out
procedure on page E14-3 to determine which is faulty.
AA
DD
CC
BB
C
A
D
B
S245710
X
Y
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