LIBRARY SOCIETY OF AUTOMOTIVE ENGINEERS, INC. 485 Lexington Avenue, New York, N. Y. 10017 Dexron Automatic Transmission Fluid Robert L. Anderson and Norman A. Hunstad Fuels and Lubricants Dept, Research Laboratories, General Motors Corp. SOCIETY OF AUTOMOTIVE ENGINEERS Automotive Engineering Congress Detroit, Mich. January 8-12,1S68 680038 Downloaded from SAE International by Purdue University, Tuesday, August 21, 2018680038 Dexron Automatic Transmission Fluid Robert L. Anderson and Norman A. Hunstad Fuels and Lubricants Dept, Research Laboratories, General Motors Corp. HISTORY OF AUTOMATIC TRANSMISSION FLUID AUTOMATIC TRANSMISSION FLUID QUALIFICATION PROGRAM - In 1937, Oldsmobile introduced the "safety au­ tomatic transmission" (1). * The engine oils first used to lubricate this new mechanism were found inadequate, and were replaced by a specially formulated lubricant which was used for initial fill and made available for service needs through Oldsmobile dealers. In 1949, a program was ini­ tiated for qualification of such fluids for sale through serv­ ice stations and other retail outlets (2). A specification was developed, and independent test laboratories were engaged to conduct most of the fluid qualification tests. The first of these laboratories was Armour Research Foundation. In the later years of the qualification program, AutoResearch Laboratories, Inc., and Southwest Research Institute conducted the tests on candidate fluids. Fluids judged qualified by the General Motors Automatic Transmission Fluid Committee * Numbers in parentheses designate References at end of paper. ABSTRACT Dexron is the new General Motors trademark which iden­ tifies currently recommended service automatic transmis­ sion fluids. The minimum quality of these fluids is higher than that of the formerly used TypeA Automatic Transmis­ sion Fluids. The new fluids will provide improved transmis­ sion operation, both initially and for extended periods of service. They may be used in servicing not only current transmission and power steering units, but also all older units for which Type A fluids were originally recommended. were identified as "Automatic Transmission Fluid, Type A." Suppliers were licensed to use the General Motors trade­ mark, "AQ-A.TF," and an assigned number in further iden­ tifying these fluids. TYPE A SPECIFICATION - The development of the Spec­ ification for Automatic Transmission Fluid, Type A dated Aug. 7, 1951 (Table 1) is reviewed in Ref. 2. Details of this specification were modified through the years as improved test techniques became available. An excellent example of this continuing development was the eventual use of the Brookfield Viscometer to measure the low temperature vis­ cosity of candidate fluids. This laboratory technique was adopted after correlation had been established between Brook- field low temperature viscosities and the performance of fluids in vehicles at low temperatures (3). The Brookfield technique proved to be much more satisfactory than the pre­ viously used low temperature evaluation methods, including the pour point test, extrapolation, paint-can pour test, and the vehicle cold room test. TYPE A, SUFFIX A MODIFICATION - In 1957, deficien­ cies in oxidation resistance of some qualified Type A fluids became evident in field service. A correlation was found between results of the Powerglide Oxidation Test, reviewed The fluids were developed principally to achieve longer shift-time retention and clutch plate durability. Advances were also made in respect to low temperature fluidity, anti- foam quality, fluid-seal compatibility, oxidation resistance,, and fluid-nylon compatability. This paper reviews the de­ velopment of the Dexron-quality fluids, and outlines the recently established specification requirements and qaulifi- cation procedures which are used to define this higher qual­ ity level for fluids supplied to the service fluid market. Do