MILFORD, MI – General Motors says its traditional 8-speed automatic transmission for the Chevrolet Corvette Stingray and coming Corvette Z06 rivals the vaunted dual-clutch 7-speed automatic gearbox in the Porsche 911, giving the automaker’s halo sports car quick shifts and improved fuel economy with bowtie value.

The rear-wheel-drive Hydra-Matic 8L90 8-speed automatic bows on the Corvette for ’15, joining the Performance Data Recorder and Valet Mode as new technologies for the coming model year. The latest-generation Z06, promising 650 hp and 650 lb.-ft. (881 Nm) of torque on top of other mechanical and exterior upgrades over the base Stingray, arrives in first-quarter 2015.

But despite the lightning-fast promise of a DCT, which German automakers favor for many performance-model products, Corvette Chief Engineer Tadge Juechter says GM will not go that direction on its all-American supercar.

There are a number of reasons, he says, starting with the fact no DCT presently exists on the market capable of handling the power output of the Z06, which will share the new 8-speed automatic with the 455-hp Stingray.

That means GM would have to design and build its own DCT to superhero specifications, and the result would be an expensive niche transmission sure to drive up costs on the value-oriented Corvette.

“One of the reasons we sell the Corvette at a reasonable price is we leverage General Motors’ (production) volume, whether it is the engine or the transmission,” Juechter tells WardsAuto during a media preview here for the 8-speed and PDR system.

GM uses a modified version of the Corvette’s 6.2L small-block LT1 V-8, redesigned for ’14, in its large pickups and SUVs. Trucks with that L86 engine will add the 8-speed in ’15 as well, moving annual production numbers for the gearbox to upwards of 700,000 units. GM historically sells fewer than 20,000 Corvettes annually.

Driveline expert ZF supplies the Porsche 911 DCT, known as Porsche Doppelkupplungsgetriebe, or PDK. Getrag lent its expertise to Ford for its small-car DCT, and Volkswagen sought out BorgWarner for the unit it uses in its namesake and Audi products.