1. INTRODUCTION With a 75 percent market share (see Figure 1 ), vehicles with transversely installed front-mounted engines represent the most common drive concept in the world. With the 8HP transmission generation, ZF has established a model range on the market that offers considerable progress with regard to fuel savings, power-to-weight ratio, and functionality. However, the gear set concept of the 8HP transmission generation is predestined for the longitudinally installed standard transmission design. A derivation as a transverse transmission leads to higher design costs and an unfavorable design that contradicts the very restricted installation spaces in the area of front-transverse transmissions. Figure 1. Transmission volumes worldwide 2013-01-1276 Published 04/08/2013 Copyright © 2013 SAE International doi:10.4271/2013-01-1276 saepcmech.saejournals.org The ZF Automatic Transmission 9HP48 Transmission System, Design and Mechanical Parts Lutz Gaertner and Michael Ebenhoch ZF Friedrichshafen AG ABSTRACT With the 8HP transmission generation, ZF established a model range on the market offering considerable progress in terms of fuel savings, power-to-weight ratio, and functionality. A front-transverse transmission derived from the 8HP transmission generation gear set concept leads to higher design costs and to an unfavorable design, contradicting the very restricted installation spaces for front-transverse transmissions. With the transmission concept of the 9HP48 transmission, the advantages of the 8HP transmission generation were successfully transferred to a front-transverse transmission design and, at the same time, all restrictions regarding the installation space were solved. Thanks to its number of gears the high efficiency and the reduced drag torque, the 9HP48 transmission delivers fuel savings of up to 16 percent compared with today's standard 6-speed automatic transmissions with front-transverse installation. The publication gives a detailed description of the mechanical design of the 9HP48 transmission. By means of a new gear set concept with 4 planetary gear sets and 6 shift elements, the requirements regarding high efficiency and a large total spread that are important for achieving fuel savings and comfort can be realized at low gear steps. For the first time, two positive locking dog clutch shift elements are applied alongside an axially parallel vane cell pump to reduce the drag torques. In order to achieve compatibility between the transmission's design and the installation spaces of typical front- transverse vehicles, a completely new transmission architecture is used. In addition to the new architecture, the achievement of installation targets is facilitated by two dog clutches, two planetary gear sets nested on top of each other, and multi-disk clutches, as well as a new torque converter design. In addition, the 9HP48 transmission is designed according to a modular principle. As a result, the basic transmission can be supplemented depending on the requirements and customer wishes. Thus, different starting elements and all-wheel drive applications can also be implemented at optimal cost in the restricted installation space conditions of front-transverse passenger cars. CITATION: Gaertner, L. and Ebenhoch, M., "The ZF Automatic Transmission 9HP48 Transmission System, Design and Mechanical Parts," SAE Int. J. Passeng. Cars - Mech. Syst. 6(2):2013, doi:10.4271/2013-01-1276. ____________________________________ 908Downloaded from SAE International by Stony Brook Univ, Monday, August 13, 2018The pressure placed upon the transmission's cost and size is even higher due to the fact that vehicles with transversely installed front-mounted engines are particularly prevalent in the cost-sensitive market of compact and mid-size cars. Against this background the development of the 9HP48 front-transverse transmission began with the search for a suitable installation space-specific gear set concept. 2. TRANSMISSION SYS