Traction Circuit - Toro Multi Pro 5800 Service Manual

Traction Circuit

The traction circuit piston pump is a variable displace-
ment pump that is directly coupled to the engine fly-
wheel. Pushing the traction pedal engages a hydraulic
servo valve which controls the variable displacement
piston pump swash plate to create a flow of oil. Pushing
the top of the traction pedal rotates the pump swash
plate to create a flow of oil for forward machine move-
ment. Pushing the bottom of the traction pedal rotates
the pump swash plate to cause oil flow for reverse ma-
chine movement. This oil flow is directed to drive the rear
wheel motors. Operating pressure on the high pressure
side of the closed traction circuit loop is determined by
the amount of load developed at the fixed displacement
wheel motors. As the load increases, circuit pressure
can increase to relief valve settings: 4000 PSI (276 bar)
in either forward or reverse. If pressure exceeds the re-
lief setting, oil flows through the relief valve to the low
pressure side of the closed loop traction circuit.
Traction circuit pressure (forward or reverse) can be
measured by installing a tee fitting and gauge into the
traction system hydraulic lines.
Multi Pro 5800
The piston (traction) pump and wheel motors use a
small amount of hydraulic oil for internal lubrication. Oil
is designed to leak across pump and motor parts into the
case drain. This leakage results in the loss of hydraulic
oil from the closed loop traction circuit that must be re-
placed.
The piston (traction) pump assembly includes a charge
pump that provides make--up oil for the traction circuit.
This gerotor gear pump is driven by the piston pump
drive shaft. It provides a constant supply of charge oil to
the traction circuit to make up for oil that is lost due to in-
ternal leakage in the piston pump and wheel motors.
Charge pump flow is directed through the oil filter and
then to the low pressure side of the closed loop traction
circuit. Pressure in the charge circuit is limited by a relief
valve located in the charge plate adapter on the rear of
the piston pump. Charge circuit pressure (250 to 300
PSI (17 to 21 bar)) can be measured at the test port lo-
cated on the tee fitting at the charge filter.
Page 4 - - 13 Hydraulic System