SOCIETY OFAUTOMOTIVE ENGINEERS, INC. 400Commonwealth Drive, Warrendale, Pa.15096 The MT644 and MT654CR Two New Automatic Transmissions ForHigh-Torque, Low-Speed Diesels A.C.HuevelDetroitDieselAllisonDivisionofGeneralMotorsCorporation TruckMeetingIndianapolis,IndianaNovember1-4,1976760840 Downloaded from SAE International by University of New South Wales, Tuesday, September 18, 2018Copyright ©Society ofAutomotive Engineers, Inc.1976 Allrights reserved. Downloaded from SAE International by University of New South Wales, Tuesday, September 18, 2018760840 The MT644 and MT654CR Two New Automatic Transmissions ForHigh-Torque, Low-Speed Diesels A.C.Huevel Detroit Diesel Allison Division ofGeneral Motors Corporation ANEW LINE offully automatic transmissions wasdesigned byDetroit Diesel Allison inthelate 1960's andearly 1970's tocover thetruck market. The transmission models within each series which were placed into production inModel Years 1971 through 1974 areillustrated inFig. 1. The AT540 Series isdesigned forusewith small bore gasanddiesel engines upto385pound feetand 235nethorsepower. TheMT600 Series isdesigned tobecompatible with large bore gasandmid-range diesels upto480pound feetand 250nethorse power. The HT700 andCLBT 750arerated at425 nethorsepower and 1220 pound feetand arede signed forusewith thelarger premium diesel engines. The transmission ratings orengine coverage of ABSTRACT Two new automatic transmissions, theMT644 andtheMT654CR, have been developed tofilla market need forusewith aclass ofheavy-duty, low speed diesel engines. Intheconcepting, planning, designing anddeveloping ofthese units, both do mestic and overseas markets were analyzed, and current vehicle factors andtrends were considered. The resulting products incorporate new orimproved features such asincreased capacity torque converter forhightorque engines, increased flowoil pump forbetter cooling, andmodulated converter lockup forgreater fueleconomy. Also goals ofmaxi mum commonality ofparts with other current transmissions andofminimum inpact onOEM in stallation requirements were achieved. Downloaded from SAE International by University of New South Wales, Tuesday, September 18, 20182 thefamily currently inproduction isillustrated in Fig. 2.Therating envelope foreach transmission is plotted asafunction oftheminimum andmaxi mum permissible engine governed speed andthe maximum input horsepower. Thesloping lines are lines ofconstant torque representing themaximum permissible input torque tothetransmissions. The basic objectives ofthenewfamily were to blanket from theClass 4through Class 8truck market, 10,000 pounds andlarger, andtominimize the automatic transmission overcost without sacrificing reliability, durability, orserviceability. These objectives were met by: Developing abasic design within each series which would meet themajor volume markets Offering optional modules orbuilding blocks that would satisfy thespecialized requirements ofthelower volume market sectors Providing maximum parts interchangeability between thethree series Keeping weight toaminimum forincreased payload TheMT644/MT654CR transmissions arenatural developments ofmarket studies thathave indicated theneed forunits with aclass ofheavy duty low speed diesel engines limited to250nethorsepower andhaving maximum engine torques of780pound feet, asshown inFig. 3.The MT644/MT654CR development programs have kept pace with the changes thathave occurred during thepast several years inboth thedomestic andoverseas markets where engines with high torque and lowspeed characteristics have become prevalent forboth economical and environmental reasons. The final determination oftheconfiguration of thetwonewmodels wasmade onlyafter athorough market study wascompleted. Thevarious transmis sion market factors -such asEuropean versus American methods ofvehicle/engine matching, use ofengine turbocharging, fueleconomy versus per formance emphasis, anduseofengine brakes wereallstudied. Also, recent trend