ZF 8HP transmission

Designed and first built by ZF's subsidiary in Saarbrücken, Germany, it first was introduced in 2008 on the BMW 7 Series (F01) 760Li sedan fitted with the V12 engine. BMW remains a major customer for the transmission. It is now in its fourth generation and has been adopted by more than 20 brands from BMW to Ram; by 2023 over 15 million units has been produced. Another major customer is Stellantis, who both received a license to produce the transmission and set up a joint-venture plant with ZF. Stellantis has built the transmission at its Kokomo Transmission plant since 2013 under their own brand name, the Torqueflite 8. The joint venture plant in Gray Court, South Carolina opened in 2012. == Specifications ==

2008: Pilot series The 8HP 70 transmission with the gearset 4 in 23-85-teeth-configuration was the pilot series and therefore without generation designation. It was first used in the BMW 7 Series (F01) 760Li, has a torque handling limit of , and weighs . 2010: 1st generation In addition to the rear-wheel drive variant, two different four-wheel drive versions were available, with a version destined for Volkswagen Group applications using a Torsen centre differential. It is able to encompass a torque range from to , and is available for use in middle-class cars through to large luxury sport utility vehicles. ZF estimated fuel economy improvement over first generation to be 3%. Refinements were also made with respect to vibration. 2018: 3rd generation Major improvements are total span of 8.59 and a fuel economy improvement of 2.5% compared to the second generation. There are several options in maximum torque available, also the gearbox is available with mild hybrid and plug in hybrid options: With and supporting boosting and recuperation in combination with 48 Volt technology up to and for usage with higher voltage. 2022: 4th generation Major improvement is the transition to a versatile modular system that allows vehicle manufacturers to comprehensively and flexibly electrify their models as required. Plug-in Hybrid options with up to and are capable of saving up to 70% of carbon emissions compared with a purely conventional variant of the 8HP according to the Worldwide Harmonised Light Vehicles Test Procedure (WLTP). In addition, a modification to gearset 3 increased the reverse gear ratio, making it less disadvantageous. With this gearset concept, the already disadvantageously large step from 7th to 8th gear is further increased, albeit only slightly. == Planetary gearset concept ==

Improved fuel economy The main objective in replacing the predecessor model was to improve vehicle fuel economy with extra speeds and a wider gear span to allow the engine speed level to be lowered (downspeeding), which is a decisive factor in improving energy efficiency and thus reducing fuel consumption. In addition, the lower engine speed level improves the noise-vibration-harshness comfort and the exterior noise is reduced. Compared to the 6-speed ZF 6HP transmission it uses 12% less fuel, and 14% less than a 5-speed transmission. Due to changes in internal design, the shift times have reduced to 0.2 seconds. Reduced manufacturing complexity In order to avoid a further increase in manufacturing complexity while expanding the number of gear ratios, ZF switched from the conventional design method—in which the planetary gearset concept was limited to a purely serial or in-line power flow—to a more modern design method that utilizes a planetary gearset concept with combined parallel and serial power flow. This was only possible thanks to computer-aided design and has resulted in a globally patented gearset concept. The resulting progress is reflected in a better ratio of the number of gears to the number of components used compared to existing layouts. The 8HP has become the new reference standard (benchmark) for automatic transmissions. Quality The ratios of the 8 gears are relatively unevenly distributed in all versions. Particularly noticeable are • the too small step between 3rd and 4th gear • and the too large step between 7th and 8th gear. This cannot be eliminated without affecting all other gear ratios. On the other hand the selected gearset concept offers 2 to 3 gears more than conventional transmissions of comparable manufacturing costs, which more than compensates for the weaknesses. Additionally, the gearset brings the ability to shift in a non-sequential manner – going from gear 8 to gear 2 in extreme situations simply by changing one shift element (actuating brake B and releasing clutch D). == Applications ==