PROPEL TRANSMISSION
SUBSECTION 9B
TROUBLESHOOTING
START-UP PROCEDURE
GENERAL
This is a closed loop system which requires the build-up of
pressures and replenishment of hydraul oil whenever any
Use the system description, Table 9B-1, and the hydraulic
component has been removed and reinstalled.
schematic (see Figure 9B-10) to isolate a problem in the
propel transmission circuit. Figure 9B-1 illustrates the
Whenever a pump or motor is replaced or air has entered
gauges and connections required for testing the hydraulic
the hydraulic Iines, use the following procedure to build
system.
system pressure and replenish fluid:
1. Fill the reservoir with the hydraulic fluid specified in Sec-
Check with the machine operator to see how the propel
transmission performed when it started to malfunction or if
tion III. The fluid should be passed through a 10 micron fil-
ter prior to entering the reservoir. Never reuse fluid.
there is anything unusual about it. Operate the propel con-
trols and check for unusual noises. Visually inspect the
2. Fill the inlet line leading from the reservoir to the pump if
propel components, looking for oil leaks. Examine the
it has drained. Check the inlet line for properly tightened
pumps and motors, reservoir, filters and all Iines, checking
fittings and make sure it is free of restrictions and air leaks.
for heat, loose connections or collapsed hoses.
3. Be certain the main pump and motor housings are filled
with clean hydraulic fluid prior to start-up by pouring fil-
TROUBLESHOOTING PROCEDURES
tered oil in the uppermost case drain port.
Some minor parts removal is required to troubleshoot the
4. Install a 600 psi pressure gauge in the charge pressure
propel hydraulic system. Cleanliness is a primary means of
gauge port of each pump.
insuring satisfactory transmission life. Cleaning parts by
5. Disconnect the electrical wires attached to the control-
using a solvent wash and air drying is adequate, provided
lers. This will allow the pumps to remain in neutral during
clean solvent is used. As with any precision equipment, the
initial start-up.
internal mechanism and related items must be kept free of
foreign materials and chemicals. Troubleshoot individual
6. Disconnect the wires at the engine fuel solenoid to pre-
components as follows:
vent the engine from starting. Jog the starting circuit until
the charge pressure reaches 80 psi at both charge pumps.
INSPECT THE PUMP CONTROLLER AND PRESSURE
OVERRIDE. The electrically actuated controller mounted on
the pump is provided with a manual controller to bypass the
electrical system and manually test the control. Discon-
nect the control wire connected to the controller and
Do not start the engine unless the pumps are in
activate the control by rotating the manual control to the left
neutral (0 swash plate angle). Take safety pre-
or right. If the machine will propel manually but not electri-
cautions to prevent machine movement in case
cally, troubleshoot the electrical control system as de-
a pump is actuated during initial start-up.
scribed in Subsection 10C.
If the machine has a tendency to propel forward or back-
ward when the controller is in neutral, the null should be
adjusted as described under the topic, Controller, later in
7. Start the engine and run it at the lowest possible rpm
this subsection.
until the charge pressure has been established. Air can be
bled from the high pressure lines by using the high pres-
The setting of the pressure override mounted on the con-
sure gauge ports on the motor manifold.
trol can be checked and adjusted. This is normally not re-
quired, however, if a problem in this area is suspected, re-
8. Once charge pressure has been established, increase
fer to the topic, Pressure Override, later in this subsection.
speed to normal operating rpm. Charge pressure should be
190-210 psi minimum. If charge pressure is not at the
proper value, shut down the engine and determine the
INSPECT SYSTEM RELIEF VALVES. When the problem oc-
cause.
curs in one direction only, interchange the relief valve cart-
9. Shut down the engine and connect the wires to the con-
ridges to see if the problem changes to the other direction
trollers. Start the engine, checking to be certain the pump
(see Figure 98-4). If so, one relief valve cartridge is either
remains in neutral. With the engine at normal operating
malfunctioning or does not have the proper setting. The first
speed, slowly check for forward and reverse machine oper-
two digits of the pressure setting are stamped on the end of
ation.
the cartridge.
10. Continue to cycle slowly from forward to reverse for
five minutes. The charge pressure should remain at 160-
180 psi minimum during forward or reverse operation.
11. Shut down the engine, remove the gauges and plug the
The relief valves are factory set and should not
ports. Check the reservoir level and add fluid if necessary.
be disassembled further.
The transmission is now ready for operation.
