SOCIETY OFAUTOMOTIVE ENGINEERS, INC. 400Commonwealth Drive, Warrendale, Pa.15096 Automatic Transmissions For Passenger Coaches R.H.Schaefer and D.L.Robinson Detroit Diesel Allison Division ofGeneral Motors Corporation Automotive Engineering Congress andExposition Detroit, Michigan February 24-28, 1975750381 Downloaded from SAE International by University of Birmingham, Sunday, August 19, 2018750381 Automatic Transmissions For Passenger Coaches R.H.Schaefer and D.L.Robinson Detroit Diesel Allison Division ofGeneral Motors Corporation RIDE SHARING ISnotnew new ontheAmerican scene. Since theearliest days ofself-propelled wheeled vehicles when bicycles built-for-two and motor cycles with sidecars were first popular many formsof multi-passengervehicles have been utilizedin the transportationbusiness. The passengercoach shownin Fig.1 wasengagedin New York City revenue servicein 1917.General Motorswas buildingcoachesas earlyas 1911,and other manufacturerssuch as YellowCoach claimed coach business heritage dating backto 1904.The V-Drive Transmission Severalpower train arrangementshave been utilized through the yearsby the variouscoach manufacturers. However, it wason July25, 1932thatthe V-drivearrangement, shownin Fig.2 wasfirstfiledfor patentby inventorDwightE. Austin.Subsequently,the first production V-drive mechanical transmission was featuredin the1935GMC Model719 GreyhoundCruiser, as shownin Fig.3. TheV-drive facilitated transverse rear engine mountingand offeredthe followingad vantages: Reducedengine compartment volume Betterservicing access to engine,transmissionand accessories Reducedoverhang over the rearaxlefor im provedaxle weight distributionand minimumtail sweepwhen turning Longerwheel base and inherentride quality advantages ABSTRACT Since the first passengercoaches were builtin theearly 1900's, coach manufacturershave sought betterand better engine-transmissioncombi nationsand arrangementsin orderto improveper formance, operation, and passenger convenience. As thecoachindustry entered the 1970's,it becameincreasinglyobvious thata needexistedfor a newtransmissionto replacethose of theold V-familythat providedthe bulkof themarketfor thepast40 years.Recognizingthe need, Detroit Diesel Allison developedtwo new transmissions,the HT740andthe V730,for the coming generationof coach applications.These two units permita numberof engine-transmission-axlearrangements and are adaptableto dieseland gas turbineengines.It isanticipatedthat these units will find wide usagein new coaches currently under development. Copyright © Societyof AutomotiveEngineers, Inc. 1975All rights reserved. Transmissionvantages: volume accessries turning reserved.Downloaded from SAE International by University of Birmingham, Sunday, August 19, 20182 These advantages were significant forthe1935 eracoaches andremain valid forthecoaches ofto day. The uniqueness oftheV-drive arrangement thus isexemplified bythefactthat itdominated coach transmission design inAmerica forthenext forty years. The evolution ofV-drives isshown in Fig. 4. Atthat same time, theBanker semi-automatic transmission was introduced inthe 1935 GMC Model 720 coach. This transmission featured an automatic centrifugal clutch, athree-speed plan etary gear setandoutput bevel gears. By1938, Spicer Models 90and 91hydraulic transmissions were introduced intheGMC Model 740coach. These units featured: Hydraulic torque converter Direct drive and countershaft reverse Output bevel gears Electro-pneumatic controls foractuating the mechanical clutches Fully automatic range selection About 1948, GMC introduced theAllison V transmission. This unit featured abevel gear set ahead ofthetorque converter rather than aftofit andincorporated other design features withrespect toitspredecessors. Assuch, theAllison Vestab lished the automatic transmission intransit coaches which have continued inpopularity forover 25years. VHand VSTransmissions -The Allison V transmission wassuperceded in1959 bytheVH model wh