SUBSECTION 9B
PROPEL TRANSMISSION
closed circuit to the second charge relief valve. This charge
2. Tolerances of working parts in the hydraulic system are
relief valve is set at a lower pressure (160-180 psi) than the
very close. Even small amounts of dirt or foreign material in
relief valve located in the charge pump. This charge relief
the system can cause wear or damage to components, as
valve limits charge pressure when the pump is in forward or
well as general faulty operation of the system. Every pre-
reverse (swash plate stroked out of neutral).
caution must be taken to assure absolute cleanliness of the
hydraulic oil.
This system provides a means of removing hot fluid from the
main closed circuit so that cooler fluid entering from the
3. Samples of hydraulic oil should be drawn from the res-
charge pump can be used to help reduce heat build-up.
ervoir every six months. These samples should be about two
quarts, and should be taken while the oil is warmed through
The shuttle valve is spring centered to the closed position so
normal operation. If possible, the sample should be
that during the transition of reversing pressures in the main
analyzed by a qualified lubrication specialist to determine
hydraulic lines, no high pressure fluid is lost from the closed
whether it is suitable for further use. The intervals be-
circuit.
tween oil changes depend on operating conditions, and on
When the pump is in neutral (0 swash plate angle) the
the care used in keeping the oil clean
manifold charge pressure should be at 190-210 psi (above
4. Whenever there is a hydraulic component malfunction
case pressure) When the pump IS in forward or reverse
which gives reason to believe that there are metal particles
(other than Oswash plate angle) the charge pressure should
or other foreign materials in the system, drain and clean the
be at 160-180 psi (above case pressure).
entire system, and replace the filter cartridges. A complete
change of hydraulic oil must be made under these circum-
stances.
Charge pressure must not be less than 160 psi
for satisfactory operation.
CONTROLLER
If the system should become contaminated,
This system uses an electric displacement controller that
DO NOT use a flushing solution to clean the
provides pump output flow (displacement) in either direc-
system. The entire system must be disassem-
tion that is approximately proportional to an electrical input
bled and cleaned.
signal. The controller has a manual input lever located on
the top of the electrical section.
5. Do not use synthetic or fire resistant oils in this system.
The packings in this system are designed for the fluid spec-
A pressure override is mounted on the electric controller to
ified in Section Ill.
provide overload protection. The override will auto-
matically destroke the pump once the desired maximum
6. All containers and funnels used in handling hydraulic oil
system pressure (load) is reached. It wiII maintain that sys-
must be absolutely clean. Use a 10 micron filtering screen
tem pressure so the load can be held. This prevents oper-
for filling the propel reservoir, and fill the reservoir only
ation of the system relief valves for prolonged periods and
through the filler opening The use of cloth to strain the oil
helps reduce lost heat build-up in the system.
should be avoided to prevent lint from getting into the sys-
tem.
An engine anti-stall feature is incorporated in the control
system. Engine speed is sensed through a magnetic pulse
7. When removing any hydraulic component, be sure to cap
pickup mounted on the flywheel housing and the throttle
and tag all hydraulic lines involved. Also plug the ports of
position through a potentiometer connected to the throttle
the removed components.
linkage A predetermined engine speed is maintained at a
9. All hydraulic components must be disassembled in spot-
given throttle positron by comparing the signal from the
lessly clean surroundings. During disassembly, pay par-
pulse pickup to the desired signal as determined by the po-
ticular attention to the identification of parts to assure
tentiometer position and, if lower than desired, reducing
proper reassembly. Clean all metal parts in a clean mineral
the voltage to the displacement controls on the pumps. This
oil solvent. Be sure to thoroughly clean all internal pass-
causes the pumps todestroke, reducing the horsepower de-
ages. After the parts have been dried thoroughly lay them
manded from the engine, thus preventing engine stall.
on a clean, lint-free surface for inspection.
Maximum tractive effort is maintained since pressure is not
9. Replace all O-rings and seals when repairing any com-
reduced.
ponent Lubricate all parts with clean hydraulic oil before
reassembly. Use small amounts of petroleum jelly to hold
MAINTENANCE
O-rings in place during reassembly.
The following points should be kept in mind when working
10. Be sure to replace any lost hydraulic oil when complet-
on the propel hydraulic system or any of the hydraulic com-
ing the installation of the repaired component.
ponents:
11. All hydraulic connections must be kept tight. A loose
1. Any structure has limits of strength and durability To
connection in a pressure line will permit the oil to leak out or
prevent the failure of structural part of hydraulic compo-
air to be drawn into the system. Air in the system can cause
nents, relief valves which limit pressure to safe operating
damage to the components and noisy or erratic system op-
values are included in the circuit. The settings of these re-
eration.
lief valves must never be changed.
