Service Manual

TractionCircuit:TractionControl
Aowdividerisincorporatedintothetractioncircuittosupplyaproportioned
owtothefront-andrear-wheelmotorsforatrue4-wheeldrivesystem.When
theHi-LospeedswitchisintheLOWpositionandyoupressthetractionpedal
intheforwarddirection,theoperatorcanengagethetractionowdividerwhen
low-tractionsituationscouldleadtowheelspin.Theengagedowdividerdivides
thetractionpumpowequallybetweenthefront-andrear-wheelmotorsto
reducethechanceofexcessiveowgoingtoaspinningwheel.
TheTEC-5001controllerdoesnotallowthetractionassisttooperatewhilethe
tractorisinthehigh-speedrangeineithertheforwardorreversedirection.The
controlleralsopreventsthetractionassistoperationinthereversedirectionwhile
themachineisinthelow-speedrange.
Thelift/lowercircuithasacounterbalancesystemtoenhancethetractioncontrol
more.Applyingaconstantpressuretothebaseendoftheliftcylindersenables
youtogetthecounterbalancetoliftthecuttingdecksasmalldistance.This
actioncausessomeofthecuttingdeckweighttobetransferredtothetraction
unittoimprovetraction.Anadjustablecounterbalancevalve(LC)inthedeck-lift
controlmanifoldcontrolstheamountofcounterbalancepressureintheliftcircuit.
TractionAssistSwitchintheOFFPosition
Inthelow-speedrangewiththetractionassistswitchintheOFFposition,the
solenoidvalve(S)inthetractioncontrolmanifoldisde-energizedtoallowthePD
cartridgespoolintheNEUTRALposition.Withthetractionpedalintheforward
direction,thehydraulicuidfromthehydrostatportMBentersthetractioncontrol
manifoldatportP ,owsthroughtheFDcartridge,andentersthePDcartridge.
FlowatthePDcartridgedividesinto2circuitsifthedownstreampressure
changes.TheowfromthePDcartridgesplitsbetweentheM1manifoldportfor
thefront-wheelmotorsandtheM2manifoldportfortherear-wheelmotors.
TractionAssistSwitchintheONPosition
Inthelow-speedrangewiththetractionpedalintheforwarddirectionandthe
momentarytractionassistswitchpressedandheldintheONposition,the
solenoidvalve(S)inthetractioncontrolmanifoldisenergizedtoallowthe
chargepressuretoshifttothePDcartridgespool.TheshiftedPDcartridge
blockstheuidowfromthehydrostat,therebypushingthehydrostatuidow
throughtheFDproportionalowcontrolvalve.Theowfromthehydrostatis
dividedapproximatelyequallybetweenthefront-andrear-wheelmotorswhile
youpressinthetractionassistswitch.
HydraulicSystem:HydraulicFlowDiagrams
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Groundsmaster5900TractionUnit
08159SLRevC