Location of Pressure Taps and Plugs
(1) Pressure tap. (2) Pressure tap. (3) Two plugs (X1 and X2).
(4) Balance lines.
Remove plugs (3) and connect a jumper hose between
the X1 and X2 ports. This makes equal oil pressure on
each side of the servo piston.
Disconnect one end of each balance line (4). Plug the
balance lines and cap the fittings for the balance lines.
Connect two 60000 kPa (8700 psi) pressure gauges to
pressure taps (1) and (2).
With the speed range switch in LOW SPEED range,
start and run the engine at 1200 rpm.
Look at the pressure gauges. The pressures on the two
gauges should be equal.
Servo Valve (Piston Pump)
If is necessary to adjust the neutral position of the
piston, loosen locknut (5). Use an allen wrench to turn
the servo valve neutral adjustment screw. Turn the
screw clockwise or counterclockwise in order to adjust
the mechanical center of the servo. The pressure on
the gauges should change. Adjust the screw until the
two pressures are equal.
Stop the engine. Remove the two 60000 kPa (8700 psi)
gauges. Replace the gauges with two 4000 kPa (580
Repeat Steps 4 through 6.
Tighten locknut (5). Remove all of the test equipment.
Install plugs (3).
Remove the caps and the plugs. Reconnect the
balance lines (4).
Perform this procedure on the axle propel pump
in the same manner. Remove the plugs and
install the jumper hose on the servo from the axle
propel pump. Read the measurements from the
pressure taps that are on the axle propel pump.
TrueTrac Differential - Test
SMCS Code: 3263-081; 3265-081
Check that the wheels on the axle of the TrueTrac
differential are driving. Make this test under load, so
that engine torque is applied through the differential with
the wheels on the ground. One way to achieve this load
is to drive up to a solid, stationary object on a dirt or on
a gravel surface. When the machine is against the
stationary object, the load can be achieved by
attempting to spin the wheels. Perform this test in
forward and reverse.
Do not operate the machine if both wheels of the TrueTrac
differential equipped axle are not driving.
Drive the machine in a tight circle. Make sure that the
machine is on a flat surface with good traction. Perform
this turn in forward and reverse in order to be sure that
the outside wheel does not scuff the ground.
disassembled. If the differential is disassembled,
tolerances may not be retained.
The TrueTrac differential must be replaced if either of
the wheels do not operate freely.