Service Manual

SteeringCircuit
A4-sectiongearpumpiscoupledtothepiston(traction)pump.Thegearpump
sectionP3supplieshydraulicowtothesteeringcontrolvalveandforthe
tractionchargecircuit.Thesteeringcontrolvalvereceivesthepumpsupplyrst,
ensuringpressureandvolumeisalwaysavailableforsteeringcontrol,nomatter
thechargecircuitdemand.Thegearpumptakesitssuctionfromthehydraulic
reservoir.Thesteeringcircuitpressureislimitedto6,900kPa(1,000psi)bya
reliefvalve(R10)locatedinthesteeringcontrolvalve.
Withthesteeringwheelintheneutralpositionandtheenginerunning,the
hydraulicowentersthesteeringcontrolvalveatthePportandgoesthrough
thesteeringcontrolspoolvalve,bypassingtherotarymeter(V1)andsteering
cylinder.TheowleavesthecontrolvalvethroughtheTporttothetransmission
oillterandtractionchargecircuit.
LeftTurn
Whenaleftturnismadewiththeenginerunning,theturningofthesteering
wheel,positionsthesteeringcontrolspoolvalvesothatowisdirectedthrough
thebottomofthespool.TheowenteringthesteeringcontrolvalveattheP
portgoesthroughthespoolandisroutedtotwoplaces.First,mostoftheow
throughthevalveisbypassedouttheTportbacktothetransmissionoillterand
tractionchargecircuit.Second,theremainderoftheowisdirectedthroughthe
rotarymeter(V1)andoutthroughtheLport.Thepressureretractsthesteering
cylinderpistonforaleftturn.Therotarymeterensuresthattheuidowtothe
steeringcylinderisproportionaltotheamountofturningonthesteeringwheel.
Theuidleavingthesteeringcylinderowsbackthroughthesteeringcontrol
spoolvalveandthenoutofthesteeringcontrolvalvethroughtheTport.
Thesteeringcontrolvalvereturnstotheneutralpositionwhenturningis
completed.
RightTurn
Whenarightturnismadewiththeenginerunning,theturningofthesteering
wheel,positionsthesteeringcontrolspoolvalvesothattheowisdirected
throughthetopofthespool.Theowenteringthesteeringcontrolvalveatthe
Pportgoesthroughthespoolandisroutedtotwoplaces.Asinaleftturn,
mostoftheowthroughthevalveisbypassedoutthroughtheTportbackto
thetransmissionoillterandtractionchargecircuit.Alsolikealeftturn,the
remainderoftheowisdirectedthroughrotarymeter(V1)butgoesoutthrough
portR.Thepressureextendsthesteeringcylinderpistonforarightturn.The
rotarymeterensuresthattheuidowtothesteeringcylinderisproportionalto
theamountoftheturningonthesteeringwheel.Theuidleavingthesteering
cylinderowsbackthroughthesteeringcontrolspoolvalvethenthroughthe
Tportandtothehydraulicreservoir.
Thesteeringcontrolvalvereturnstotheneutralpositionwhenturningis
completed.
HydraulicSystem:HydraulicFlowDiagrams
Page4–30
Groundsmaster
®
4300-D
16226SLRevD