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AT06 AT Fluid.pdf

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AT06 AT FLUID
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80 TOYOTA Technical Training wTransmits engine torque wControls hydraulic system wApplies clutches and brakes wLubricates moving parts wRemoves heat from internal parts wCleans 1. Describe the purpose for the following oil additives: a. Viscosity index improver b. Oxidation inhibitors c. Anti-foaming agent d. Corrosion inhibitors 2. List the three types of ATF and their application in Toyota automatic transmissions. 3. Identify automatic transmission fluid conditions and their cause. Section 6 AUTOMATIC TRANSMISSION FLUID Lesson Objectives:AUTOMATIC TRANSMISSION FLUID Automatic Transmissions - Course 262 81 Theautomatictransmissionhydraulicsystemrequiresspecialfluidfor thetransmissiontooperateproperlyandprovidealongservicelife.A filterisusedtocleanthefluidandpreventwearanddamagefrom occurringtothecomponentsofthetransmission.Anoiltowatercooler isalsoprovidedintheradiatorofthecoolingsysteminordertoremove excessiveheatfromthefluid.Inaddition,sincetheenginecooling systemreachesoperatingtemperaturequickerthanthetransmission, thecoolerhelpstowarm-upthetransmissionfluid. Automatictransmissionfluidisahigh-gradepetroleumproduct containingseveralkindsofspecialchemicaladditivesandis abbreviatedasATF.Thisfluidplaysvariousimportantfunctionsinthe automatictransmission.Itispressurizedbythetransmissionoilpump andfedtothetorqueconverterandtransmitsthetorquegeneratedby theenginetothetransmission.ThepressurizedATFflowsthroughthe passagesandvalvestooperatetheclutchesandbrakesthatcontrolthe planetarygearsandothermovingparts.Inadditionitcools,cleansand lubricatesallmovingparts. Inordertoperformallthesefunctionsforthousandsofmilesand deliversatisfactoryperformance,anumberofadditivesareusedto dealwiththeenvironmentofclosetolerances,highheatandrotating components. ATFissubjectedtoawiderangeoftemperaturesfrom-77 5Fto338 5F. Whentemperaturesarelow,viscosityincreasesandATFdoesnotflow well.Asaresult,shifttimingmaybedelayed,slippageatbandsand multipledischoldingdevicesmayoccur.Ontheotherhand,ifthe temperatureistoohot,thefluidthinsoutandthelubricationfilmmay breakdown,causingmetaltometalcontactandwear.Therefore viscosityisoneofthemostimportantfactorsaffectingATF’sabilityto operatethetorqueconverter,valvebodycomponentsandtheholding devices.ATFincludesaviscosityindeximprovingagenttomaintain viscosityathightemperaturesandpourpointdepressantstoimprove lowtemperatureflowability. ATFtemperaturesreacharound212 5Fatnormalspeedsandupto about300 5Fundersevereoperatingconditions.Thesurface temperatureofclutchdiscmayheatupto660 5Formore.Therefore ATFmusthavegoodthermalresistance.Ifitdoesnot,deterioration duetoheatcausesachemicalreactiontooccur,leadingtogreater oxidationofitsoilmoleculeswhichcausesformationofvarnish,sludge andacidswhichleadstointernaldamage.Oxidationinhibitorsare usedtocombatheatrelatedfluidbreakdown. Function of ATF ATF Additives Viscosity Thermal and Oxidation StabilitySection 6 82 TOYOTA Technical Training ATFisviolentlychurnedandshearedbetweentheimpellerand turbineinthetorqueconverter.Duringperiodsofhighvortex,the shearingofATFcreatesatremendousamountofheat.Thechurning andshearingoffluidcausesittofoamasairismixedwiththefluid. Foamreducespressureandpromotesslippage,wearandoxidationof thefluid.Ananti-foamingagentisaddedtoATFtopreventairbubbles andreducethelifespanofbubblesthatdoform. Waterandoxygencauserustformationoretchingofmetal components.Corrosioninhibitorsareaddedtocoatandadheretometal componentsandpreventmoisturefromaccumulatingandcausing damage. ThreetypesoffluidhavebeenusedinToyotaautomatictransmissions. TypeTisthelatesttypetobeusedandisfoundinAll-Tractransaxles (A241HandA540H).TypeFwasusedinearlyToyotaautomaticsup untilAugust1982.AllfrontenginefrontdrivetransaxlesusedDexron II.InJuly1983allToyotatransmissions,frontwheeldriveandrear wheeldriveusedDexronII. ATF Used by Toyota w Type ”T” All-Trac Transaxles A241H & A540H w Dexron II All Toyota Automatic Transmissions since 1984 (except All-Trac) Prior to 1984 — A55 (1983), A41, & A140 w Type ”F” All Toyota Automatic Transmissions prior to 1984 Whilecheckingthefluidlevel,theconditionofthefluidshouldbe evaluated.Theconditionofthefluidcantellyouaboutwhatcanbe expectedinsidethetransmissionandmayconfirmthetestdrive symptoms. Ifthefluidisdarkreddishbrownorbrown-blackandsmellsburnt,this mayindicatethatthefluidhasnotbeenchangedatproperintervals. Removingthepanmayreveallargeamountsofsediment,indicatinga failedmultiplateclutchorbrake.Flakesinthefluidindicateamassive internalfailure. Defoaming Characteristics Corrosion Inhibitors ATF Types Fluid ConditionAUTOMATIC TRANSMISSION FLUID Automatic Transmissions - Course 262 83 Ifthefluidismilkycolored,coolantismixedwiththeATF.Inadvanced stages,theenginemayoverheatandyouwillfindoilinthecoolant system.Insomecases,watermayenterthetransmissioncasethrough thebreathercapordipsticktubeduetofloodingordrivinginadverse weatherconditionswithafillertubethathasnotbeencappedwiththe dipstick. Aeratedfluidcanbecausedbylowfluidlevelorhighfluidlevelas discussedearlier.Smallbubbleswillcoverthedipstickasan indicationofthiscondition.Inadvancedstages,itwillcauseoxidation andvarnishbuildup.Airiswhippedintothefluidandheatwillcause thefluidtooxidize.Varnishbuild-upwillcausethevalvesinthevalve bodytostick. Asaruleofthumb,transmissionfluidshouldlast100,000milesifthe operatingtemperatureremainsnohigherthan175 5F.Forevery20 degreesoftemperatureincrease,theprojectedservicelifeofthefluidis cutinhalf.Forexample,ifoperatingtemperatureisallowedtoremain at195 5F,theservicelifeofthefluidwouldbe50,000miles.Section 6 84 TOYOTA Technical Training
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