2020-01-0438 Published 14 Apr 20 20Development of GM Allison 10-Speed Heavy Duty Transmission Chi Teck Lee, David Ames, Brett Caldwell, Matthew Knoth, Timothy Reinhart, Jeffrey Kelly, Rajesh Kannan, and German Tanasi General Motors LLC Citation: Lee, C.T., Ames, D., Caldwell, B., Knoth, M. et al., “Development of GM Allison 10-Speed Heavy Duty Transmission,” SAE Technical Paper 2020-01-0438, 2020, doi:10.4271/2020-01-0438. Abstract This paper describes the development of the GM Allison 10-Speed Heavy Duty (HD) Transmission. The trend of increased towing capacity and engine horsepower in the automotive heavy-duty truck segment has been steadily climbing for the past 10 years. The development of 10-Speed HD Transmission is designed to be best in class in for towing performance in the 2500/3500 series segment while opti - mizing fuel economy. The 10-Speed HD Transmission also gives the customers the option to order an integrated power take-off (PTO) unit that benefits downstream installation of utility accessories such as hydraulic pumps, generators, etc. Introduction The 10-Speed HD Transmission is designed with the proven winning recipe of the GM Allison 6-Speed HD history. The 10-Speed HD Transmission can produce much higher output torque than the 6-Speed HD Transmission enabling significantly higher gradeability even while towing operation ( Figure 8 ). It also has increased towing capability of 35,500 lbs. (16,103 kg) with a standard final drive ratio of 3.42 ( Figure 1 ). In addition, the 10-Speed HD Transmission is the first in the industry to be able to handle up to 43,500 lbs. (GCVW) in the 3500 series HD truck segment when it is properly equipped [ 1]. The enhanced towing and launching performance do not compromise fuel economy to the customer. Lastly, the current 6-Speed HD Transmission add-on turbine driven PTO (Power Take-Off) has been upgraded to an integrated engine driven live PTO option (Figure 10 ) using a chain driven compact design, and it is available for the first time ever as an OEM factory installed option [ 2]. All enhanced features are designed and packaged within the same space claim as the current GM Allison 6-Speed HD generation. Overview of GM Allison 10-Speed HD Transmission The 10-Speed HD Transmission consists of a 320  mm diameter torus torque converter, four simple planetary gear sets (GS1, GS2, GS3, GS4), two brake wet friction clutches (C1, C2), four wet friction rotating clutches (C3, C4, C5, C6), an engine driven off-axis hydraulic gear pump with variable displacement, hydraulic control valve body and a park system. The stick diagram ( Figure 2 ) and lever diagram (Figure 3 ) show the interconnection nodes of planetary gear  FIGURE 1   Comparison of major heavy-duty applications available during 2018-2020 period for towing capacity vs available final d rive ratio matching.© SAE International; General Motors.  FIGURE 2   GM Allison 10-Speed HD Stick Diagram. © SAE International; General Motors.Downloaded from SAE International by Tsinghua University, Thursday, April 23, 2020DEVELOPMENT OF GM ALLISON 10-SPEED HEAVY DUTY TRANSMISSION 2 sets and clutches. There are four hydraulic energized clutches and two open clutches per gear stage in the 10-Speed HD Transmission powerflow. The clutching table ( Table 1 ) provides the clutching element combination that define each gear state of the 10-Speed powerflow. The stick diagram has the key components identified in the cross-section. (Figure 10 ) The torque converter turbine side output spline connects to the turbine shaft; the turbine shaft is spline connected to the input planetary carrier; the S1 shaft is spline connected to S2; the reaction planetary carrier and R4 are spline connected by PC1-R4 Triple Rotating Clutch Housing; the R2 gear and S3 gears are spline connected by the R2-S3 shaft; the R3 is spline connected to the welded S4 gear hub; the park gear is located on the output planetary carrier node and the output shaft i