SOCIETY OFAUTOMOTIVE ENGINEERS, INC. TwoPennsylvania Plaza,NewYork,N.Y.10001 TheTruckAutomatic andVehicleEconomics J.F.HittleandA.R.Schuette DetroitDieselAllison DivisionofGeneralMotorsCorporation WestCoastMeeting Anaheim,Calif. August12-16,1974740618 Downloaded from SAE International by University of Bath , Sunday, September 23, 2018740618 TheTruckAutomatic andVehicleEconomics J.F.HittleandA.R.Schuette DetroitDieselAllison DivisionofGeneralMotorsCorporation Inthelast25years,theemphasis incommercial transport servicehasshiftedfromrailtoroad.Asa resultofthisshift,truckownershavebeencon frontedwiththeproblemofoperating increasingly sophisticated, heavier,fastervehiclesovermore demanding dutycycles,inthefaceofashortageof skilleddrivers,whileunderthepressureofcosts outrunning prices.Since1956,manytruckowners haveutilizedtheAllisonMTSeriesautomatic transmission tosuccessfully copewiththisproblem bymakingthelesserskilleddrivermoreproductive, thus,moreprofitable. Onthebasisoftheex perience gainedwiththatfirstgeneration automatic transmission, Detroit DieselAllison releasedtoproduction in1970theAT-540-thefirst ofafamilyofthreeautomatic trucktransmissions fortheentirecommercial truckindustry. Thesuccessofthefamily,asmeasured bygreateraccep tanceinexistingmarketsandsignificant penetra tionintonewmarketareas,furtherconfirmsthe facttheautomatic trucktransmission hasbeen satisfying thetruckmarket's changing andin creasingly diverserequirements totheeconomic benefitofthevehicleowner. Now,duetothecurrentenergycrisis,spiraling wagesandinflation, fleetownersareagainreassess ingtheirtotalvehiclecosts.Thisreassessment necessarily includesanevaluation ofeachvehicle component anditsattendant costcontribution to thetotalsystem.Asaresult,fleetownersarefin dingtheautomatic trucktransmission hasmatured asaneconomic assettothemeventotheextentof providing, contrarytopopularbelief,fueleconomy comparable tothatofamanualtransmission. Inan ABSTRACT Becauseoftheincreasing complexity ofcommercial trucking operation andmanagement, thetruck automatic transmission isbeingfoundtobean assetintermsofoverallvehicleeconomics-inad ditiontoitslongrecognized features ofeaseof operation andsafety.Anumberofsalientvehicle costfactorsuponwhichthetruckautomatic transmission hasanimpactarediscussed-along withthetransmission designprinciples whichleadtothatimpact.Acceptance ofthispremisebythe truckingindustry isshownbymarketsegment. Inadditiontodiscussing thecontribution ofthe truckautomatic transmission towardimproving the overalleconomics positionoftoday'scommercial vehicles,thispapergivesindication offorthcoming refinements intransmission designwhichwill furtherreducefuelconsumption costs. Copyright ©Society ofAutomotive Engineers, Inc.1974 Allrightsreserved. Downloaded from SAE International by University of Bath , Sunday, September 23, 20182 efforttoexamine furthertheeffectsofthe automatic trucktransmission onthecommercial truckingindustry, thispaperwillcoven •Salientvehiclecostfactorsuponwhichthe automatic transmission hasanimpact,andthe designprinciples thatcausetheautomatic transmission tobeaviable,costeffectivecom ponent. •Acceptance oftheautomatic transmission by thetruckingindustry,marketsegmentbyseg ment. •Transmission refinements, evaluated viafield, simulated andengineering vehicletestdataas favorablyimpacting fueleconomy,particularly fortheover-the-road segment. VEHICLE COSTFACTORS ACQUISITION COSTS-Detroit DieselAllison recognizes thattheautomatic trucktransmission generally represents aninitialover-cost-a costin excess ofthevehicle's standard manual transmission-in mostapplications. However, in concepting anddeveloping thenewfamilyof transmissions, asshowninFig.1,minimum over costanditsrapidrecoveryweretargetted formal objectives inadditiontothenormalreliability, service,durability andlifeobjectives. Theseobjectives weremetby: •Developing aversatile, basicdesignwhich wouldmeetthevolumemarketrequirements •Offeringdesignintegrated optionsthatwould satisfythespec