With the supercharged V8 under the hood of the 2017 Camaro ZL1 putting out 640 horsepower (477 kW) and 640 pound-feet (868 Nm) of torque, Chevrolet has designed a new 10-speed automatic transmission to handle all of that power going to the rear wheels. This new gearbox is no slouch, offering faster shifting than that found in a Porsche PDK dual-clutch.
The new automatic houses 10 gears, six clutches, and a 7.39 overall gear ratio spread, all in a housing that is about the same size as the outgoing eight-speed automatic and six-speed gearbox option. Although sport buyers may prefer a manual transmission, the power ratios, fast shifting, and fuel economy gains from the new 10-speed in the 2017 ZL1 may help change a few minds.
According to Chevrolet, in tests the new Hydra-Matic 10-speed transmission improves on upshift times over the legendary Porsche PDK dual-clutch – often considered a benchmark in automated sports car transmissions – by 36 percent from first to second gear, 27 percent from second to third, and 26 percent from third to fourth.
What's more, gear ratios in the new Chevrolet 10-speed are extremely aggressive in the lower gears and then very refined in the upper gears, offering a lot of torque conversion for the rear wheels at the beginning and then refinement and speed maintenance towards the top. The gear spread allows the Camaro ZL1 to be aggressive off the line and then maintain speeds when cornering and maneuvering at pace.
The first gear ratio is 4.70:1, up from 4.56 in the previous-generation eight-speed. Second gear is at 2.99:1 (up from 2.97), third at 2.15 (vs 2.08), fourth at 1.80 (vs 1.69), fifth at 1.52 (vs 1.27), sixth at 1.28 (vs 1.0), seventh at 1.00 (vs 0.85), eighth at 0.85 (vs 0.65), ninth at 0.69, and tenth at 0.64. For spin doctors who love to flip their cars out of a reverse burnout, the reverse gear is at a happy 4.87:1.
Several engineering tricks were used to keep the Hydra-Matic 10-speed lightweight and compact. The first was to house the entire thing in a one-piece aluminum case with an integrated bell housing. The turbine clutch torque converter in that bell is 260 mm around. The torque converter features a lock-up clutch and an electronically controlled capacity clutch (ECCC) to dampen engine pulses. The ECCC gives a regulated amount of slip in the drivetrain in non-sport shifting to cushion gear shifts and smooth the ride.
Six clutches are housed inside the transmission, two for braking and four rotating clutches for shifts. That is one more clutch than the outgoing eight-speed, made possible thanks to a new triple-clutch assembly in the middle of the transmission's architecture. Also important in keeping all of this running smoothly is a newly-designed variable-displacement vane pump and a specially-formulated low-viscosity transmission fluid.
Gear shifting is executed with a clutch-to-clutch movement, allowing one clutch to engage as another disengages. When gears are skipped, such as in rapid slowing for corners, a freewheeling change is made instead, using a synchronized mesh.
Finishing this new Hydra-Matic 10-speed's fast-paced shifting is a new Chevrolet-designed shift control box, which is not integral to the transmission. This control unit includes what Chevy calls Performance Algorithm Shifting, which monitors engine use and adapts shift patterns according to the driver's style.
Manual shifting through steering-mounted paddles switches the control box to Driver Shift Control. This makes for fast response to driver input while protecting against over-revs in down-shifting without taking shifting duties over from the driver – a common complaint in some other "manual mode" automatics.
To boost efficiency, the new transmission fluid in the Hydra-Matic 10-speed is run through an internal thermal bypass to allow faster warmup times for the transmission.
The new Hydra-Matic transmission will be built in General Motors' newly-upgraded Romulus, Michigan plant, with Chevrolet saying it plans to incorporate this transmission into eight additional models in the next two years.Source:
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