INTRODUCTION Automatic transmission technology for passenger, light duty and heavy duty vehicles continues to evolve to meet increasingly stringent greenhouse gas (GHG) emission regulations, see [ 1] for example. As with any transmission system, a balance between size, mass, cost, number of gear states, number of shifting elements, type of launch device and the requirements of the application for acceleration, fuel economy and shift quality must be made. A report prepared for the EPA, [ 2], indicated the incremental cost and performance improvements for AT technology to transition from 6-speeds to 8-speeds as a key enabler to reducing GHG emissions. An approximate 2 to 6% reduction in CO 2 emissions was the reported benefit in [ 3] by implementing leading edge transmission technologies. Over the past decade, the number of fixed gears states for step gear planetary ATs have steadily increased, with 6-speeds common place and 8- speeds gaining more market volume, [ 4 and 5], demonstrating the reported incremental improvements in performance. Six and seven speed dual clutch transmissions (DCT's) have emerged in the past few years as an alternative type of AT due to their favorable energy usage and ratio tuning potential over planetary type AT, [ 2, 6, 7 and 8]. A search for relevant intellectual property reveals a multitude of unique planetary and multi-input shaft parallel axis gear transmissionpowerflows with 8 or more gears states, utilizing 5 or more clutching elements, see [ 9, 10, 11, 12, 13, 14, 15, 16] as representative examples. The aim of these designs are to leverage the kinematic design of the gearbox to optimize gear ratios and progression while minimize parasitic losses to reduce GHG emissions without sacrificing acceleration performance or drive quality. The TCT design presented in this paper is based upon these motivating principles. The goal of this investigation is to introduce the TCT design concept primarily as an 8-speed and compare its performance relative to an 8-speed planetary AT with torque converter and leading edge technologies. The attributes of acceleration, both launch and passing, parasitic torque loss, energy usage and fuel consumption will be explored in detail using energy analysis based upon the vehicle-powertrain system. For the analysis conducted in this investigation, an inline four cylinder, boosted gasoline engine of 2.0L displacement and a peak torque output of 350 Nm is utilized in a 1530 kg rear wheel drive (RWD) vehicle. TRIPLE CLUTCH TRANSMISSION 8-Speed Powerflow The basis of the transmission kinematic design is derived from a two stage DCT design, with an added input shaft and a two speed output on each countershaft. There are three 2013-01-9042 Published 12/15/2013 Copyright © 2013 SAE International doi:10.4271/2013-01-9042 saeeng.saejournals.org Performance Characterization of a Triple Input Clutch, Layshaft Automatic Transmission Using Energy Analysis Darrell Robinette General Motors Company ABSTRACT This paper details the design and operating attributes of a triple input clutch, layshaft automatic transmission (TCT) with a torque converter in a rear wheel drive passenger vehicle. The objectives of the TCT design are to reduce fuel consumption while increasing acceleration performance through the design of the gearing arrangement, shift actuation system and selection of gear ratios and progression. A systematic comparison of an 8-speed TCT design is made against a hypothetical 8-speed planetary automatic transmission (AT) with torque converter using an energy analysis model based upon empirical data and first principles of vehicle-powertrain systems. It was found that the 8-speed TCT design has the potential to provide an approximate 3% reduction in fuel consumption, a 3% decrease in 0-100 kph time and 30% reduction in energy loss relative to a comparable 8-speed planetary AT with an idealized logarithmic ratio progression. CITATION: Robinette, D., "Performance Characterization of