Five years ago, Ford and GM decided to put their differences aside and work together on a pair of transmissions. Ford would develop a 10-speed for rear-wheel-drive vehicles and GM would work on a nine-speed for front-wheel-drive applications.

According to a report from Automotive News, though, GM's nine-speed just doesn't return the fuel-economy benefits that would make its extra weight worthwhile, so Ford will be using their own transmissions instead.

The transmissions, to be fair, haven't exactly been a boon to fuel economy. The 2017 Chevrolet Malibu, which uses the transmission, only gets one more MPG than the previous generation, which used an eight-speed gearbox.

The Buick Envision, meanwhile, actually loses an MPG on the highway. According to the EPA, the 2019 model gets 25 MPG whereas the 2018 model got 26 MPG with a six-speed transmission.

That squares with Ford's argument that it's not seeing any fuel economy gains, but GM argues that there's more to a transmission than saving fuel.

"We've engineered our nine-speeds for even more refined shifts," said GM spokesman Tom Read in a release. "Smaller steps between gears in a nine vs. an eight-speed enable smoother shifts for customers."

Thanks to its wider gear ratio, GM argues, its cars get better off-the-line acceleration, something most shoppers are looking for. GM also argues that the smaller steps between gears helps give its cars smoother, "almost imperceptible" upshifts, and a more premium feel, as a result.

Ford wasn't interested in those improvements, though, as Automotive News reports that it decided not to use the nine-speed transmission before any GM cars hit the market with it.

"The small efficiency benefit did not justify the added weight and cost of an extra clutch and gear," Ford's Mike Levine told Automotive News.

Instead, Ford will go back using another product of a Ford-GM collaboration, the six-speed trans first designed in 2002 (among other transmissions), because of its light weight and ability to handle torque.

[source: Automotive News]