Monday, September 5, 2016

10 Things to Know About the New Ford/GM 10-Speed Automatic Transmission

-This new 10-speed rear-drive transmission is the result of collaboration between Ford and General Motors, although Ford had the engineering lead on it. The companies also are jointly developing a nine-speed transverse automatic for front-drive cars and crossovers; GM is leading the engineering on that effort. Not long after Ford starts cranking out F-150s with these transmissions, Chevrolet will launch it in the 2017 Camaro ZL1, coupled to the 650-hp, supercharged 6.2-liter LT4 engine from the Corvette Z06. With a torque capacity of at least 650 lb-ft, this first version of the transmission is plenty beefy to handle that track-ready machine, as well as the Ford Raptor, with its uprated 3.5-liter EcoBoost V-6 making upwards of 450 horsepower—maybe more. We would expect that soon afterward, we will see this design spawn a family of 10-speed automatics that are smaller and lighter to suit less-hunky rear-drive machines in the Ford and GM families.-As you’d expect, Ford’s new 10R80 10-speed automatic has a wide spread of ratios between first and tenth gear. However, the overall span of 7.384 is not the widest in the business—not by a long shot. There are at least five conventional automatics, including some eight-speeds, with a wider spread. The widest is the front-drive ZF 9HP series with nine gears, as found in the Jeep Cherokee, with a total spread of 9.819. Porsche’s PDK seven-speed dual-clutch gearbox used in the Panamera goes even further with a maximum spread of 10.119. According to Kevin Norris, Ford’s manager of the 10R programs, in the applications planned for this transmission, extensive simulations indicated that there was no benefit in a span wider than 7.4. And with a top gear that isn’t excessively tall, it’s possible to stay in that gear more often at highway speeds, something that we’ve found nearly impossible to achieve with the Jeep Cherokee’s tall ninth gear.-Arithmetic dictates that if the 10-speed transmission does not have a particularly wide overall ratio spread, than the individual gear spacing must be fairly close. Sure enough, with the 10R80, the average rpm drop during a shift is only 20 percent, while it’s 25 percent in the ZF eight-speed found in cars across the industry, and 32 percent in Porsche’s seven-speed PDK. This new 10-speed has closer ratios, on average, than the version of the seven-speed PDK in the latest 911 GT3. The tight ratios keep the engine closer to peak power during full-throttle acceleration and, according to Norris, provide for smoother operation when towing a trailer, a matter of some importance in the F-150 world.-Tenth gear in the 10R80 transmission has an overdrive ratio of 0.636. Ninth is 0.689. That’s a drop of only eight percent, making for a nearly imperceptible 10-to-9 downshift when needed. While Norris promises that tenth gear is a genuinely useful gear in the F-150 and the transmission will stay in that gear over a wide range of highway conditions, the close ninth ratio helps when the truck is heavily loaded or towing a substantial amount. The transmission also offers “Tow/Haul” and “Sport” modes, which also usefully employ the ninth gear—almost as an alternative top gear. Eighth gear also is an overdrive, with a ratio of 0.854.-Though much of the initial hype about this transmission centers on its installation in Ford’s upcoming new Raptor and the Camaro ZL1, it will first go on sale in the 2017 F-150 that's coupled to the upgraded version of the Ford 3.5-liter EcoBoost V-6, which now makes 375 horsepower and 470 lb-ft of torque. The 10R80 will be standard equipment with that engine and its close ratios nicely match the engine’s copious low-rpm torque. On the EPA city cycle, the F-150 with this powertrain never sees engine rpm exceed 1450 rpm. In other words, plan to get much worse real-world fuel economy. Although, when you step into it, Ford claims the transmission and engine controls coordinate carefully to avoid situations where the engine comes onto boost exactly when the transmission downshifts, thereby providing a larger jolt of acceleration than the driver wanted.-Thanks to the use of four simple planetary gearsets, controlled by six clutches, the 10R80 is only about an inch longer and four pounds heavier than the 6F55 transmission currently used with the 3.5-liter EcoBoost V-6. This required very careful attention to detail in the design of each component. For example, the torque converter in the transmission (pictured above) is about 0.4 inch thinner and two pounds lighter than the one in its predecessor. Part of the weight reduction comes from an aluminum stator support, a formerly cast-iron part. In fact, the new transmission has no cast-iron parts whatsoever.-The clutches in an automatic transmission are hydraulically actuated and controlled, so the new transmission relies on two special pumps to provide the necessary hydraulic muscle. The main pump is an off-axis design with variable displacement. Removing the pump from the transmission’s main shaft reduces overall length; the variable-displacement capability means that the pump’s output can be adjusted to the transmission’s needs, reducing the power that the pump absorbs. A second, electrically driven hydraulic pump allows idle-stop capability. The electrically driven pump is both more reliable and more compact than a hydraulic accumulator, while using very little power.-Just as engine oil seems to get thinner every year, so does transmission fluid, in search of reduced friction. Back when four-speed automatics were the norm, transmission fluid had a viscosity of around 7.5 centistokes. The Ford six-speed uses fluid with a viscosity of 6.0 centistokes. The new 10-speed drops that to about 4.5 centistokes, reducing both friction and the workload of the hydraulic pumps. The new fluid is called Mercon ULV, and is planned to last the lifetime of the transmission, aided by a new filter that has two levels of high-efficiency media and a pleated design with much greater area than the filter in the current six-speed transmission. It also helps that the transmissions are assembled in factories that set new industry standards for cleanliness.-With a low first-gear ratio of 4.696, the torque converter basically aids in a smooth launch, then quickly locks up and stays that way. Shifting is controlled by the six clutches, which engage and disengage two at a time to swap cogs swiftly and smoothly. These shifts do not require the torque converter to unlock, which would decrease efficiency. These clutches are controlled by integrated solenoid valves, which respond more quickly than the usual two-piece designs. The system has also been designed to minimize the length of the hydraulic passages and optimize the clutch designs for quick fill times—all in the interest of faster and more responsive clutch operation. Although we’re skeptical, and these kinds of claims are heavily dependent on exactly what constitutes the start and end of a shift, Ford claims transmission shifts 26 percent–36 percent more quickly than Porsche’s PDK, at least through fourth gear. The transmission can also perform large, multi-gear downshifts—directly from tenth to fifth, or ninth to fourth—smoothly and rapidly. There’s also a one-way clutch, which smoothly and cleanly disengages the transmission when rolling to a stop, avoiding a potentially jarring 3-1 downshift.-In addition to the efficient hydraulic pumps and the low-viscosity fluid, there are other measures to reduce the transmission’s mechanical friction. For example, instead of flat thrust washers, the 10R80 uses ones fitted with radial needle bearings, replacing sliding friction with the lower rolling variety. Even the multi-plate clutches get tiny springs which push the plates apart to minimize their drag when they are not engaged. As a result, the new transmission is more efficient in each of its gears than the six-speed it replaces.-For all of these improvements in friction reduction, low-viscosity fluid, and the multiplicity of gears, Ford is only claiming very modest fuel economy improvements for the new transmission. Compared with the existing six-speed automatic, Ford suggests a 3-percent-to-4-percent gain—barely a single mpg in the case of the F-150. That’s very odd, because when ZF introduced its eight-speed automatic, the company claimed an 11-percent fuel-economy improvement over its existing six-speed automatic. Aisin claimed a 6.6-percent-to–7.0 percent improvement with its eight-speed automatics, while Mercedes suggests a gain of up to six percent when going from the 7G-Tronic to the 9G-Tronic. Ford is adding four gears rather than two, yet only expecting half as much benefit. Perhaps Ford is engaging in a serious bit of under-promising here. We would be shocked to see less than 2-mpg-to–3 mpg of improvement once the ’17 F-150 is certified—especially because the truck also gets that improved version of the 3.5-liter EcoBoost V-6.–
from Car and Driver BlogCar and Driver Blog http://www.caranddriver.com/flipbook/10-things-to-know-about-the-new-fordgm-10-speed-automatic-transmission
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