SOCIETYOFAUTOMOTIVE ENGINEERS, INC. TwoPennsylvania Plaza,NewYork,N.Y.10001 TheAllison AT-540Automatic Transmission inUtilityTruckApplications A.R.Schuette DETROIT DIESELALLISON DIVISION GENERAL MOTORS CORPORATION NationalCombined FuelsandLubricants, Powerplant andTransportation Meetings St.Louis,Mo. October25-29,1971710658 Downloaded from SAE International by University of Birmingham, Monday, August 20, 2018710658 TheAllisonAT-540Automatic Transmission inUtilityTruckApplications A.R.Schuette DETROIT DIESELALLISON DIVISION GENERAL MOTORS CORPORATION INTRODUCTION InSeptember, 1970,theDetroitDiesel AllisonDivisionofGeneralMotorsintro ducedtheAT-540four-speed fullyautomat ictransmission formedium-heavy duty trucks. TheAT-540marksthefirstauto matictransmission specifically designedfor single-drive axletrucksinthe10,000to 36,000poundGVWrange.(SeeFig.1.) Thispaperdescribes brieflytheevolution of thisnewheavydutyautomatic, discusses the specifications andfeatures, and,morespe cifically,emphasizes thecharacteristics whichmaketheAT-540uniqueforutility truckapplications.Inthedesignanddevelopment oftheAT-540 transmission, significant emphasiswas placedonconsideration ofthevocational requirements towhichitwillbeapplied. Often,thephilosphy ofdesigningforthe majororhighvolumeusersprecludesmeet ingtherequirements ofthelowvolumeus ers.Thisphilosophy wasnotusedinthe designanddevelopment oftheAT-540. Carefulconsideration wasgiventothere quirements ofeachofthevocationsinwhich itwillbeapplied(Fig.2).Eventhoughthe utilityindustryconstitutes arelativelysmall percentage ofthetotalnumberofvehiclesin the10,000to36,000poundGVWrange,more thanaverageconsideration wasgiventoutil itytruckrequirements inthedesignofthe AT-540. ABSTRACT September, 1970markedtheintroduction of thefirstautomatictransmission designed specifically forsingle-drive axletrucksand busesinthe10,000to36,000poundGVW class.Thisnewproductisdesignated the AT-540fourspeed,fullyautomatictrans mission. Afterthebackground onthedevel opmentoftheAT-540ispresented, thebasic designfeaturesandgeneralapplications are defined. Theconsiderations ofthevocations inwhichitwillbeappliedarethendiscussedasrelatedspecifically toutilitytrucks.This includespowertakeoffrequirements, vehicle performance, andinstallation. Verification ofthecompatibility oftheAT-540transmis sionispresented withspecificreference to thetestprogramconducted, pilotvehicle operation, andproduction testing.The AT-540hasprovenitselftobeadurable, worthwhile component ofvehiclesforthe utilityindustry. Downloaded from SAE International by University of Birmingham, Monday, August 20, 20182 Background Eventhoughtheneedforsuchaproducthad longbeeninevidence, theconfiguration of theAT-540andareasofpreciseintended application werenotsoapparent. Tobetter understand theseneeds,theDetroitDiesel AllisonDivisionconducted extensiveengi neeringandmarketstudiestobetterdeter mineanddefinewheresuchaproductwould fit,aswellastomoreprecisely define thoseneedstheproductwouldhavetofulfill forittobetrulymarketable. Oneofthesemarketsegments whichwas closelyanalyzedwasthatoftheutilityindus try.Itistheapplication ofthisnewproduct tothetrucksrequiredbytheutilityindustry towhichtheattention ofthesedataaredi rected. MarketStudies Initially,marketjudgements andengineer ingevaluations weremadefrommeetings withpeoplerepresenting allfactionsofthis areaofinterest. Thisincludedutilitybody manufacturers, chassismanufacturers, powertakeoffdrivemanufacturers, and mostimportantly, theenduser-theutility. Inaddition,experience fromtheapplication oftheAllisonMTseriestransmission to thisindustrysince1956wasthoroughlyre searchedandprovedtobeextremelybene ficialinnewdesignconsiderations.Development Thedataobtainedfromthesemarketstudies andthatfromothermarketing areasprovid edabaselineforacomprehensive engineer ingstudyinthedevelopment ofaproduct whichwouldnotonlymeetgeneraltruckand busrequirements withintheapplicable GVW range,butwouldalsoallowforspecificap plicationdemandsoftheutili