What’s behind IS important
Coupled to the new 1.6-liter diesel squeezed into the new GMC Terrain, Chevrolet Equinox and Cruze is an allnew 9T50 9-speed automatic transmission, a transmission that was jointly developed with Ford and first used in the 2017 Chevrolet Malibu. It is Chevrolet and GM’S first 9-speed.
Why nine speeds instead of six? Fuel economy, launch, passing, and NVH. The new nine-speed has a very wide overall ratio of 7.6:1. That’s far greater than the outgoing six-speed’s 6.0:1. A benefit often overlooked is the first gear launch, now 4.69. With the torque of the new diesel, it should deliver a very solid stoplight getaway. And the top gear at 0.62, an overdrive gear, coupled with the same available torque will make highway cruising both economical and smooth. It will also contribute to less noise while on the highway.
With smaller steps between gears the new tranny will have “smooth, almost imperceptible upshifts, for excellent refinement,” said Dan Nicholson, Vice President Global Propulsion systems at GM. “No matter the engine torque or vehicle speed, the 9T50 is always in the perfect gear.”
Development focused on transverse-layout vehicles, front-wheel drive—a 10-speed for RWD vehicles was also co-developed—and all gears are lined up with the crankshaft. The 9T50 also uses GM’S first application of a selectable one-way clutch that can hold torque or freewheel depending on operating mode. Five planetary gearsets are used, along with four stationary clutches and three rotating clutches. GM says that saves space and increases smoothness.
Other features include new torque converter technology featuring a hyper-elliptical oval cross-section. This reduces the thickness of the torque converter, keeping the overall width narrow for packaging. The transmission also employs stop-start technology and a hydraulic accumulator keeps the gears ready to go the moment your foot leaves the brake.