Toro 04384 Service Manual

Also see for Greensmaster 3250-D: Operator's manual Quick start guide Operator's manual Operator's manual Operator's manual

Contents

Greensmaster 3250--D Hydraulic SystemPage 4 -- 13Traction CircuitsForwardThe piston (traction) pump is driven directly by the en-gine. The traction circuit of the hydraulic system acts es-sentially as a closed loop. Taking its suction directly fromthe return side of the wheel motors of the traction circuit,the piston pump supplies oil flow to the wheel motorsthrough the supply side of the traction circuit.With the engine running and traction pedal in the neutralposition, the piston pump supplies no flow to the wheelmotors. When the traction pedal is pressed to the for-ward position, the linkage from the pedal positions theswash plate in the piston pump so oil flows out the topport of the pump. Oil flow out of the top port goes to thewheel motors and turns them in the forward direction.Oil flowing out of the wheel motors returns to the bottomport of the piston pump and is continuously pumped outthe top port as long as the traction pedal is pressed forthe forward direction.Hydraulic oil is supplied to the traction charge circuitfrom the rear gear pump section though the steeringvalve, control manifold and back through the charge cir-cuit check valves in the piston (traction) pump. This oilreplaces oil losses from flow through the internal casedrain, shuttle valve and small amounts of traction circuitleakage. Charge circuit pressure is maintained by thecharge relief valve that is attached to the piston pumpback plate.ReverseThe traction circuit operates essentially the same in re-verse as it does in the forward direction. However, theflow through the circuit is reversed.With the engine running and traction pedal in the neutralposition, the piston pump supplies no flow to the wheelmotors. When the traction pedal is pressed to the re-verse position, the linkage from the pedal positions theswash plate in the piston pump so oil flows out the bot-tom port of the pump. Oil flow out of the bottom port goesto the wheel motors and turns them in the reverse direc-tion.Oil flowing out of the wheel motors returns to the top portof the piston pump and is continuously pumped out thebottom port as long as the traction pedal is pressed forthe reverse direction.The charge circuit functions the same in reverse as itdoes in the forward direction.Traction Circuit CoolingThe piston pump includes a shuttle valve that bleeds offa small amount of hydraulic fluid for cooling of the closedloop traction circuit. This valve allows a small amount ofhydraulic oil to pass from the low pressure side of thetraction circuit while operating the traction unit in eitherdirection. A relief valve in the piston pump back plateprevents shuttle valve bleed off until the relief valveopens (70 to 100 PSI / 5 to 7 bar). The charge circuit re-plenishes oil that is bled from the traction circuit by theshuttle valve.NOTE: The shuttle valve assembly is located in the pis-ton pump back plate. Access to the shuttle valve re-quires removal of the back plate from the piston pump.HydraulicSystem