Over the course of the past several years, German manufacturer ZF Friedrichshafen has introduced 8- and 9-speed transmissions. Vehicle models from the likes of Chrysler and Land Rover have made use of the new hardware, touting fuel economy gains and other advantages. Now, the other two major Detroit auto manufacturers are teaming up to develop 9-speed transmissions of their own, and they're taking it one step further: 10-speed transmissions.

GM and Ford announced on Monday that they are cooperating on the development of 9- and 10-speed transmissions toward better vehicle performance and improved fuel economy. The transmissions will eventually make their way to front-wheel and rear-wheel drive cars, crossovers, trucks and SUVs across both manufacturers' line-ups.

"Engineering teams from GM and Ford have already started initial design work on these new transmissions," said Jim Lanzon, GM vice president of global transmission engineering. "We expect these new transmissions to raise the standard of technology, performance and quality for our customers while helping drive fuel economy improvements into both companies’ future product portfolios."

While such a team-up between two rival-giants might seem strange, automakers work jointly on projects all the time – the Toyota FT 86/Scion FR-S/Subaru BRZ being a well-known recent example. Such partnerships help to pool resources, save costs and speed development.

GM and Ford state that this marks the third time in 10 years that they're collaborating on transmissions. Both companies together have delivered more than 8 million jointly developed 6-speed front-wheel-drive transmissions, including on popular models like the Ford Explorer and Chevrolet Malibu.

GM and Ford will build the transmissions at their own respective plants and independently match them to individual vehicles, but they will use common, interchangeable hardware.

At March's Geneva Motor Show, Land Rover showed what it called the world's first 9-speed transmission (the ZF HP9) on a passenger car. Ten-speed transmissions remain a technology of the future.

"Ten-speeds put them ahead," Jim Hall, analyst at 2953 Analytics LLP, told the Detroit News. "People now are working on eights and nines. Tens are on the bleeding-edge side."

Based on past public comments, ZF won't be rushing to compete against Ford and GM. In November, its CEO Stefan Sommer suggested at the Automobilwoche Congress in Berlin that more than nine gears could exceed the point of diminishing returns. He said that the added weight and complexity of more gears would eliminate the fuel economy advantages.

A Ford spokesperson told us that technological advances over the past few years have helped to cut internal drag losses, thereby reducing the penalty for adding more gears and empowering enough potential fuel economy increase to make developing a 10-speed worthwhile. He clarified that the 10-speed is being designed for rear-wheel-drive applications and could be particularly well-suited to trucks

GM declined to provide a technical response to Sommer's comments and said that they were not making executives available for interview. A spokesperson stated simply that the comments are Sommer's opinion and reiterated the general goals of improved performance and increased fuel economy.

Of course, ZF had a shiny new 9-speed transmission to advertise when Sommer made those comments, and rumors of 10-speeds from the GM-Ford partnership and Hyundai were already circulating at the time. We don't see GM and Ford putting the work into development without some solid perceived gains. How successful they'll be at realizing those gains remains to be seen.

Sources: Ford/GM, Autoweek