Abstract Toyota Motor Corporation developed the Multi Stage Hybrid System for the Lexus flagship LC500h coupe with the aim of achieving an excellent balance between fuel economy and acceleration performance. The Multi Stage Hybrid Transmission used in this new hybrid system includes a shift device located immediately the power split device and motor. Compared with existing hybrid systems, acceleration performance is improved by increasing the driving force at low and medium vehicle speeds in lower gears, fuel economy and heat management performance are improved by reducing electrical loss by selecting the optimal gear depending on the driving state. The Multi Stage Transmission uses a shift device with a wide gear ratio range to maximize both fuel economy and acceleration performance. The transmission was designed to achieve the appropriate size to be mounted in a new platform, as well as class-leading low noise levels for adoption in luxury vehicles. This is a key development item for Lexus vehicles which must meet high customer expectations in terms of silence characteristics, specifically in hybrid transmissions, due to the various components with backlash, which can lead to various rattling noises. This paper describes the technology developed to reduce rattling noise in the Multi Stage Hybrid Transmission. 1. Introduction In 2006, Lexus introduced the GS450h, equipped with the Lexus Hybrid Drive (LHD) system developed for rear-wheel drive (RWD) passenger vehicles. This system was later adopted for the all-wheel drive LS600h in 2007 as well. At the core of system was the hybrid transmission with a two-stage motor speed reduction device [ 2]. While providing superior fuel economy, the acceleration performance of this hybrid system is also highly regarded by drivers of competing vehicles. Since the introduction of these vehicles, various refinements have been applied to the hybrid transmission, adding to the already major contributions made towards reducing CO 2 emissions. However, in recent years, increasing awareness of environmental pollution has created growing demand for various types of low-emission vehicles, as even more stringent emissions regulations are being announced across the globe. In an effort to develop and popularize vehicles with even higher environmental performance, automakers around the world have been actively developing ecofriendly vehicles, and a wide range of systems have been launched. Competition in the market has never been higher. Even in the luxury coupe market, dominated by vehicles with excellent dynamic performance, hybridization has become a trend, as still higher levels of fuel economy and acceleration performance are in demand. To achieve supreme balance between fuel economy and acceleration performance in the RWD coupe market, Toyota has developed the Multi Stage Hybrid System. By combining this system with a V6 engine, the all new LC500h achieves a 0-to-60 mph time of 4.7 seconds and 30.0 mpg of combined fuel economy, all the while meeting SULEV requirements for exhaust emissions. At the core of this system is the newly developed Multi Stage Hybrid Transmission, including a shift device located immediately after the power split device and motor. 2. Development Objectives One of the main focus points in the development of the new Multi Stage Hybrid Transmission was to secure equivalent noise and vibration characteristics as the current model LS600h, equipped with the L110 series transmission, while achieving even higher levels of fuel efficiency and acceleration performance.Rattling Noise Reduction Technology for Multi Stage Hybrid Transmission2017-01-1157 Published 03/28/2017 Hiroyuki Tateno, Yuji Yasuda, Masatoshi Adachi, Haruhisa Suzuki, Tomoaki Furukawa, Koji Hayashi, and Shohei Nagata TOYOTA MOTOR CORPORATION CITATION: Tateno, H., Yasuda, Y ., Adachi, M., Suzuki, H. et al., "Rattling Noise Reduction Technology for Multi Stage Hybrid Transmission,