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.[1][2] The joint venture plant in Gray Court, South Carolina opened in 2012.[3]
The 8HP is the first transmission to use this 8-speed gearset concept. In the meantime it has become the new benchmark for automatic transmissions.
The GM 8L transmission is based on the same globally patented gearset concept. While fully retaining the gearset logic, it differs from this only in the patented[4] arrangement of the components with gearsets 1 and 3 swapped.[5]
^Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
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 700 N⋅m (516 lb⋅ft), and weighs 87 kg (192 lb).[6]
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.[7] It is able to encompass a torque range from 300 N⋅m (221 lb⋅ft) to 1,000 N⋅m (738 lb⋅ft), and is available for use in middle-class cars through to large luxury sport utility vehicles.[7]
Since gearset 4 meshes in almost all gears up to and including 5th gear, large gear wheels are advantageous for durability. As the very high ratio 1st gear is formed exclusively by gearset 4, its sun gear is unusually small. For this reason, this gearset was enlarged by over 20 % when the 1st generation was introduced, even if this advantage had to be given up again immediately when the 2nd generation was introduced in order to increase the total span.
2014: 2nd Generation
Efficiency improvements over the pilot design and the first generation include a wider ratio span of 7.81, reduced drag torque from the shift elements, reduction in required oil pump pressure, and broadened use of the coasting and start-stop systems.[8] 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 15 kW (20 hp) and 200 N⋅m (148 lb⋅ft) supporting boosting and recuperation in combination with 48 Volt technology up to 90 kW (121 hp) and 250 N⋅m (184 lb⋅ft) for usage with higher voltage.[9]
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 160 kW (215 hp) and 280 N⋅m (207 lb⋅ft) 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).[10] 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.
Progress Gearset Concept
Main Objectives
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). Compared to the 6-speed ZF 6HP transmission it uses 12 % less fuel, and 14 % less than a 5-speed transmission.[11][12] Due to changes in internal design, the shift times have reduced to 0.2 seconds; additionally, the unit 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).[13]
Extent
In order to increase the number of ratios, ZF has abandoned the conventional design method of limiting themselves to pure in-line epicyclic gearing and extended it to a combination with parallel epicyclic gearing. 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.
^ abcdefInnovation Elasticity Classifies Progress And Market Position
Automobile manufacturers drive forward technical developments primarily in order to remain competitive or to achieve or defend technological leadership. This technical progress has therefore always been subject to economic constraints
Only innovations whose relative additional benefit is greater than the relative additional resource input, i.e. whose economic elasticity is greater than 1, are considered for realization
The required innovation elasticity of an automobile manufacturer depends on its expected return on investment. The basic assumption that the relative additional benefit must be at least twice as high as the relative additional resource input helps with orientation
negative, if the output increases and the input decreases, is perfect
3-speed transmissions with torque converters have established the modern market for automatic transmissions and thus made it possible in the first place, as this design proved to be a particularly successful compromise between cost and performance
It became the archetype and dominated the world market for around 3 decades, setting the standard for automatic transmissions. It was only when fuel consumption became the focus of interest that this design reached its limits, which is why it has now completely disappeared from the market
What has remained is the orientation that it offers as a reference standard (point of reference, benchmark) for this market for determining progressiveness and thus the market position of all other, later designs
All transmission variants consist of 7 main components
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 one 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.
^Der neue BMW M760 Li xDrive · BMW Medieninformation Deutschland (The new BMW M760 Li xDrive · BMW Media Information Germany) · 02/2016 · p. 23 · and Der neue BMW M760 Li xDrive · Technische Daten · BMW Medieninformation Oesterreich (The new BMW M760 Li xDrive · Technical Specifications · BMW Media Information Austria) · 01/2017 · p. 2 · 800 N⋅m (590 lb⋅ft)[17][16]
^narrow total ratio span · preferebly for petrol engines, sports cars, and high performance engines · Alpina B3 Saloon AWD · Technical Data · 730 N⋅m (538 lb⋅ft)[18][16]
^Technical specifications · The new BMW 3 Series Sedan · BMW Media Information · 03/2019 · p. 2: BMW 320i Sedan · 300 N⋅m (221 lb⋅ft)[19][16]
^loc. cit. · p. 10: BMW M340i xDrive Sedan · 500 N⋅m (369 lb⋅ft)[19][16]
^wide total ratio span · preferebly for Diesel engines, offroad cars, and low performance engines · loc. cit. · p. 18: BMW 330d Sedan · 580 N⋅m (428 lb⋅ft)[19][16] and Alpina D3 S Saloon AWD · Technical Data · 730 N⋅m (538 lb⋅ft)[20]
^narrow total ratio span · preferebly for petrol engines, sports cars, and high performance engines · The first-ever BMW XM · Market launch September 2022[21][22] The all-new BMW M5 · Market launch June 2024[23][24]
^wide total ratio span · preferebly for Diesel engines, offroad cars, and low performance engines · Progress and efficiency with added variety: additional drive system variants and innovations for the new BMW 7 Series · Market launch 2022/2023[25][26] Alpina XB7 AWD · Technical Data[27]
^w/o hydraulic torque converter · narrow total ratio span of 4.2[28]
^based on the same gearset concept as the 8HP transmissions[29][30]