aElva The EngineeringResource ForAdvancing Mobility 400 COMMONWEALTH DRIVE WARRENDALE, PA 15096 821277 The Allison Transmission Output Retarder S.F. Spurlin and J.L. Trotter Detroit Diesel Allison Division of General Motors Corporation Truck and Bus Meeting Indianapolis, Indiana November 8-12, 1982Downloaded from SAE International by University of New South Wales, Wednesday, September 19, 2018The appearance of the code at the bottom of the first page of this paper indicates SAE's consent that copies of the paper may be made for personal or internal use, or for the personal or internal use of specific clients. This consent is given on the con- dition, however, that the copier pay the stated per article copy fee through the Copyright Clearance Center, inc., Operations Center, 21 Congress Si, Salem, MA 01970 for copying beyond that permitted by Sections 107 or 108 of the U.S. Copyright Law. This consent does not extend to other kinds of copying such as copying for general distribution, for advertising or promotional purposes, for creating new collec- tive works, or for resale. Papers published prior to 1978 may also be copied at a per paper fee of S2.50 under the above stated conditions. SAE routinely stocks printed papers for a period of three years following date of publication. Direct your orders to SAE Order Department To obtain quantity reprint rates, permission to reprint a technical paper or per- mission to use copyrighted SAE publications in other works, contact the SAE Publica- tions Division. ISSN 0148-7191 Copyright 1382 Society of Automotive Engineers, Inc.Downloaded from SAE International by University of New South Wales, Wednesday, September 19, 2018821277 The Allison Transmission Output Retarder S.F. Spurlin and J.L. Trotter Detroit Diesel Allison Division of General Motors Corporation MARKET STUDIES HAVE INDICATED a desire for sec- ondary braking systems on both trucks and buses. This desire is worldwide with two major purposes being considered; to control speed during down- hill operation and to increase service brake life on duty cycles with high stop densities. The downhill braking requirement is centered pri- marily in Europe where long, steep mountainous grades with switchback curves are commonplace. In order to meet upgraded European braking stan- dards, and to increase vehicle service brake life, the Allison integral output retarder was conceived. The design and development of this output retarder integrally designed as an option with the MT600 series transmission and adaptable to the V730 and 1iT700 series Allison automatic transmissions is the subject of this paper. RETARDER REQUIREMENTS The criteria used in the design and develop- ment of the Detroit Diesel Allison integral out- put retarder was established to provide a total braking package. Sufficient capacity was re- quired for vehicle braking on long, steep moun- tainous grades while maintaining enough capacity at lower vehicle speeds for maneuvering around switchback curves. In addition, the retarder should supplement the vehicle service brakes dur- ing the stop/start type duty cycles resulting in significant life extensions of the brake components. Specific requirements which were considered based on discussions with various original equip- ment manufacturers and end users include:o Capacity to meet legal requirements for vehicle braking on a grade. A typical European requirement is to maintain 30 km/h (19 mph) on a 7 percent grade for 6 km (4 mi). o Capacity in the normal speed range of city bus applications to have a significant im- pact on vehicle service brake wear. o Capacity in descending high speed grades for maximum vehicle controllability while leaving the service brakes in reserve. o Capacity to support a total vehicle stop- ping rate of .1 g down to low speeds where capacity can be reduced for smooth transi- tion to the vehicle service brakes as a complete stop is made. o Initial braking response should be fast and smooth (no resultant