ABSTRACT Shengrui Transmission Limited Corporate (Shengrui) has developed a new 8 speed automatic transmission (SR 8AT) for front wheel drive (FWD) vehicle. The concept of SR 8AT is unique and different from the conventional automatic transmission. The design of the SR 8AT system and components are new and compact. By combining an innovative gear train which is similar with the conventional manual transmission and the simple planetary gear structure, SR 8AT achieved 8 speed with the shortest length of the FWD transmission, the competitive fuel economy and the smooth shift performance among comparable automatic transmissions. INTRODUCTION In the last decade, the energy resources and the environmental issues such as the auto emissions have become increasingly important to the automotive industry and even to the economy of the World. The emission regulation and the energy policy from the governments in different Countries have forced the automakers to produce the vehicles with superior fuel efficiency and cleaner exhaust gases while improving basic performance characteristics like acceleration time and NVH. As a solution to meet these requirements, Shengrui has designed and developed the new SR 8AT with the new technology for the usage of SUVs and sedans in China. Figure 1 shows Shengrui automatic transmission product line with the torque range of the engines. Shengrui has developed and is developing the automatic transmissions not only to adapt to the engine torques, but also appeal to more customers and obtain better fuel economy by expanding the product line from the SR 8AT 300 Nm up to SR 8AT 300 Nm hybrid, SR 8AT 400 Nm and down to SR 8AT 200 Nm. These transmissions are capable of handling the torque between 100 Nm and 400 Nm and offering greater satisfactions in powertrain match and vehicle performance. Figure 1. Shengrui Automatic Transmission Product Line As shown in Figure 2, SR 8AT adopts a compact and efficient gear train which was concepted by Dr. Peter Tenberge and awarded to Shengrui as Outstanding Patented Invention by Chinese State Intellectual Property Office and World Intellectual Property Organization in 2011. The gear train structure consists of 5 shifting elements, 3 sets of spur gears and 3 sets of simple planetary gears for 8 well stepped forward gears and 1 reverse gear. By combining the gear train with the precise controls of the clutch to clutch and the lower drag friction discs, SR 8AT achieves an outstanding fuel economy among the comparable automatic transmissions. The fuel economy of the vehicle equipped with SR 8AT is improved by 6 % or more comparing to conventional 4 and 6 speed transaxles.The Design, Development and Industrialization of an New 8 Speed Automatic Transmission in China2013-01-1277 Published 04/08/2013 Jan Gang Lu SAIC Shengrui Transmission Copyright © 2013 SAE International doi:10.4271/2013-01-1277Downloaded from SAE International by University of British Columbia, Wednesday, August 01, 2018Figure 2. SR 8AT Concept Schematic OVERALL DESIGN The arrangement of the gear train with both spur gear sets and simple planetary gear sets allows the compact design of SR 8AT with 365 mm in length and the lower weight with 5 kg less than the comparable 6 speed transmission. The conventional one way clutch (OWC) is not used in the design and the spur gear set takes place as the role of OWC along with the control of clutch to clutch. The differential gears and the set of primary speed reduction gear are packaged well with the suitable ratio of the differential in the overall design. The cross section of SR 8AT is shown in Figure 3. The transmission oil pump is connected directly to the engine. Engine power is directed through a torque converter to the transmission input. The valve body and controls are packaged in the transmission sump. SR 8AT offers a wide range of features which are summarized as following: All wheel drive availability, TCC availability 1 st - 8th gears, Skip shifting, R