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DRIVETRAINDIAGNOSIS1STEP2CHATFTN0201AJInspect4WDSystem&TransferPERFORMANCE:•Beabletodescribetheoutlineofthe4WDsystem.•Beabletodescribethevarious4WDoperationsystems.•BeabletoinspectandmeasurethetransfertypeTX12.RESOURCES:Thefollowingresourceshavebeenpreparedforthismodule.•TransferunitTX12model•GeneraltoolsandSST(fillergauge,gearpullersanddrifts)OBJECTIVECHA0396DRIVETRAINDIAGNOSIS2STEP2CHATFTN0201AJ•BeabletoinspectandmeasurethetransfertypeTX12.SKILLCHECKDRIVETRAINDIAGNOSIS3STEP2CHATFTN0201AJCONTENTS1.FOURWHEELDRIVESYSTEM1)FunctionoftheSystem2)SystemType3)Featuresof4WD4)Disadvantagesof4WDSystem2.TRANSFER1)ConstructionTypeofTX12Transfer2)FunctionofTransfer3)TransmissionofTorque(TX12type)4)FeaturesofShiftPositions5)TransferforFFBasedVehicleHere’swhatyoudo....(1)6)GearComponentInspection(TX12modeltype)7)InspectionPointsHere’swhatyoudo....(2)3.VISCOUSCOUPLING1)GeneralDescription2)CenterDifferentialSKILLCHECKTARGETAbilitytogotoanESMtopicdestinationAbilitytodescribethefunctionofthetransfersystemAbilitytodescribetheoutlineofthefourwheeldrivesystemIfyoufeelconfidentaboutyourknowledgeandskillsofthesetasks,youcanproceedtothenextmodule.Askyourcourseinstructorforguidance.AbilitytounderstandthemeasurementandinspectionpointsofthetransfersystemAbilitytounderstandtheviscouscouplingsystemDRIVETRAINDIAGNOSIS4STEP2CHATFTN0201AJ1.FOURWHEELDRIVESYSTEM1)FunctionoftheSystemThefourwheeldrivesystemisasystemthatdeliverstheenginetorqueforboththefrontandrearwheels.Itisgenerallycombinedwithatransfermechanism.Enginetorquedistributedforthefrontandrearwheelscanprovidebetterdrivingperformance,stabilityanddrivability,especiallyonslipperyroads.Thedifferenceabsorptionoftherotationspeedbetweenthefrontandrearwheels,whichoccurswhencorneringduetothedifferenceofthefrontandrearwheels,iseliminatedusingadifferentialfunctionandadrivetrainpartitionfunction.2)SystemTypeCLASSIFICATIONThedrivingsystemofa4WDvehicleisdividedintotwocategories,part-time4WDandfull-time4WD.Moreover,thefull-time4WDisclassifiedintotwotypesbythetorquedistributionsystembetweenthefrontandrearwheels.PART-TIME4WDCHA0398ENG.T/MT/F2WD4WDFrontdifferentialReardifferentialENG.T/MT/FFrontdifferentialReardifferential(Rearwheeldrive)(All-wheeldrive)CHA03974WDPart-time4WDFixedtorquedistributiontypeVariabletorquedistributiontype(ALL-Mode4WD)Full-time4WDDRIVETRAINDIAGNOSIS5STEP2CHATFTN0201AJFeaturesWiththepart-time4WDsystem,avehicleisnormallydrivenbytwofrontorrearwheels.Asnecessary,the4WDsystemcanbeselectedbytheshiftingleveroraswitch.TorquedistributionEnginetorqueisalwaysdistributedinafixedratiotothefrontandrear(mostlyinthe50:50ratio).Torquedistributionisproportionaltothedynamicweightdistributiononthefrontandreartiresifallfourtiresareontheroadsurfaceandhavethesamefrictionalcoefficient.Evenifoneofthefrontorreartiresslips,thesameenginetorqueasinthenormalconditionistransmittedtotheothertiresandthevehiclegetsthesametractionbasedoneachtiregripcondition.FULL-TIME4WDCHA0400CHA0400ENG.T/MFrontdifferentialgearViscuscouplingViscuscouplingViscuscouplingCenterdifferentialgearReardifferentialgearT/FDRIVETRAINDIAGNOSIS6STEP2CHATFTN0201AJFixedtorquedistributiontypeWiththefull-time4WDsystem,avehicleisalwaysdrivenbyallfourwheels.Thistypegenerallyhasacenterdifferentialsystemthatdistributestheenginetorquetothefrontandtherearwheelstoabsorbthedifferencebetweenthefrontandrearwheelrotations.Somemodelsadoptaviscouscouplingasalimitedslipdifferentialtomaintaintractionatalltimes,contributingtobetterstabilitywhenoneofthefrontorrear,orrightorleftdrivewheelslipsonaroughroadorslipperyroad.VariabletorquedistributiontypeEnginetorqueisdistributedinavariableratiotothefrontandrearwheelsaccordingtotheroadand/ordrivingcondition.ALL-Mode4WDThe4WDcontrolunitappliestodrivethefrontaxleasrequiredviathemultiplediscclutchinstalledinthetransferunit.WhenthesystemissetintheAUTOmode,thefrontandreartorquedistributionisoperatedbyhydraulicpressureorelectromagnetismandchangesfromarangeof0:100(reardrivemode)to50:50(full-time4WDmode)accordingtotheroadsurfaceconditions.CHA0401DRIVETRAINDIAGNOSIS7STEP2CHATFTN0201AJ3)Featuresof4WDThefollowingfourfeaturesaretheadvantagesofa4WDsystemcomparedtoa2WD(FWDorRWD)system.Accordingtothetypeof4WDsystem,eachadvantageappearsdifferently,significantlyorrarely.BETTERRUNNINGPERFORMANCEOnavehiclewitha2WDsystem,thedrivetiresmayeasilysliporraceinslipperyconditionssuchasonsnowyorroughroads,especiallyfortheroadconditiononwhichthefrictionalcoefficientofeachtirebecomesdifferent.Ifonesideofthedrivetiresrotates,anothersideofthetirewillstopduetothefunctionofthedifferentialsystem.Onavehiclewitha4WDsystem,thetireishardertoslipthanthatof2WDsystembecausetheenginetorqueisdistributednottojusttwowheelsbuttoallfourwheels.BETTERACCELERATINGPERFORMANCEItishardertoslipdrivetiresonavehiclewitha4WDsystemthanthatwitha2WDsystemwhenaccelerating.Thisisbecausetheenginetorqueisdistributedtoboththefrontandrearwheelsinawell-balancedcondition,resultinginasmallerdrivingforceofeach4WDdrivingwheelthanthatof2WD.Thiscontributestobetterstartingstabilityandperf