Hydraulic Flow Diagrams; Traction Circuit (Machine Serial Number Below 316000000) - Toro Groundsmaster 3280-D Service Manual

Hydraulic Flow Diagrams

Traction Circuit (Machine Serial Number below 316000000)

Forward Direction
Groundsmaster ® 3280-D/3320
05138SL Rev B
The hydrostatic transmission input shaft is rotated by a driveshaft off the front of
the engine crankshaft. Pushing the top of the traction pedal rotates the variable
displacement pump swash plate in the transmission to create a flow of fluid. This
fluid is directed to the fixed displacement motor in the transmission which turns
the front axle input shaft to drive the front wheels in the forward direction.
Fluid flowing from the motor returns to the variable displacement pump and is
continuously pumped through the closed traction circuit as long as the traction
pedal is pushed.
A gerotor charge pump in the hydrostat provides a constant supply of charge
fluid to the closed loop traction circuit for lubrication and to make up for fluid that
is lost due to internal leakage in the transmission pump and motor. The charge
pump takes its suction through a filter from the reservoir (front axle). Charge
pump flow is directed to the low pressure side of the closed loop traction circuit.
Charge pressure is limited to 482 to 1,034 kPa (70 to 150 psi) by the charge
pressure relief valve in the transmission. Charge pressure can be monitored at
the transmission charge pump test port. Charge pump flow in excess of traction
circuit charge needs provides hydraulic flow for the steering and lift circuits.
Page 5–19 Hydraulic System: Hydraulic Flow Diagrams