GM's eight-speed gearbox isn't quite ready for prime time.

General Motors is set to join the the multi-speed gearbox race with the launch of a new eight-speed automatic next year. Some of GM's first eight-speed products will use an Aisin-sourced unit, but the Detroit automaker will eventually switch completely to its own eight-cog design.

According to Motor Trend, most of GM's vehicle lineup will benefit from Cadillac's need for an eight-speed gearbox. Cadillac needs an eight-speed to better take on rivals like BMW and Mercedes-Benz, and that technology will eventually spread through most of the automaker's lineup.

GM is currently designing its own eight-speed box for both longitudinal and transverse applications (or rear-wheel/all-wheel drive and front-wheel drive/all-wheel drive in layman's terms), but development of the former won't be done in time to launch for the 2014 model year. In order to hold the company over without losing any more ground to the competition, GM has reportedly inked a year-long agreement with Aisin for one of its eight-speed designs.

The Aisin-designed eight-speed will likely debut in the all-new Chevrolet Corvette in early 2013, but will quickly spread to the Cadillac ATS and the new CTS. It remains possible that GM could use the Aisin-sourced gearbox in its new range of full-size pickups as well.

Once GM totally signs off on its own eight-speed gearbox, it will phase out the Aisin unit.

There is still no concrete date on when we will see GM's front-wheel drive eight-speed auto on the road, but the new gearbox will likely debut in the Cadillac XTS within the next 18 months. From there it should spread to the Chevrolet Impala and Buick LaCrosse, with the rest of the automaker's lineup in play thereafter.