eaThe Engineering— Resource ForAdvancing Mobility 400 COMMONWEALTH DRIVE WARRENDALE, PA 15096 SAE Technical Paper Series 811285 A Fuel Efficient Automatic Four-Speed Transmission for Light Trucks R. I. Green Chevrolet Engineering Dept. Truck Meeting Dearborn, Michigan November 9-12, 1981Downloaded from SAE International by University of New South Wales, Monday, September 17, 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 St., 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 $2.50 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 O 1981 Society of Automotive Engineers, Inc.Downloaded from SAE International by University of New South Wales, Monday, September 17, 2018811285 A Fuel Efficient Automatic Four-Speed Transmission for Light Trucks R. J. Green Chevrolet Engineering Dept. WITH THE GROWING IMPACT OF FUEL ECONOMY REGULATION on light trucks and escalating fuel costs, GM's efforts to increase efficiency in light trucks have included an improved transmission. The automatic unit that evolved is the subject of this paper. This transmission, the first of the integral designs, provides.features considered necessary for specific Chevrolet vehicle programs being planned. From the beginning it was considered ideal for construction by a GM facility currently assembling the THM 350C trans- mission, because of components that are common. Therefore the Chevrolet-Toledo plant, producer of the current THM 350C, was chosen as the manufacturing source for the new transmission. Over the past few years, Toledo has encouraged the use of aluminum on many transmission components, and its application of new manufacturing techniques for the production of alu- minum components is evident in this transmission. DESCRIPTION The THM 700-R4 transmission (Fig. 1), was originally designed for a torque capacity of 700 Nm input to thegear box in vehicles up to 3900 kg (8600 Ibs) GVW. Subsequent testing showed the unit to be suitable for use with engines of higher output and vehicles of greater potential weight, depending on type of duty. The unit features 2 simple planetary gear sets coupled to give 4 forward speeds and reverse (Fig. 2). Significant features of the transmission are: •298 mm diameter torque converter and clutch •Variable capacity vane pump with 390 aluminum housing and cover •390 aluminum die cast input housing •Seven position manual control quadrant with 3 braking ranges •Converter clutch flexibility (can be applied in any' gear and/or speed). •Shift pattern control flexibility. The unit weighs 83.4 kg (184 Ibs) including 11 liters of transmission fluid. The THM 350C which it replaces' weighs 82.5 kg (182 Ibs). The THM 700-R4 represents the first 4-speed over- drive integral unit produced by GM. Earlier 4-speeds were reduction units, while the most recent addition to the GM automatic transmission line, the THM 200-4R, is ABSTRACT One phase of the broad General Motors program to improve fuel economy has been the design of an integral 4-speed automatic transmi