The modern automotive business is a funny thing, making bedfellows of the unlikeliest of couples.

Ford and General Motors don't collaborate often, but when they do it's usually on a transmission. This tradition continues as both companies announce an agreement to co-develop new 9- and 10-speed automatic transmissions, aimed at increasing the efficiency of their vehicles.

It's the third time in a decade the two companies have co-developed transmissions, previously working on a six-speed automatic for front-wheel drive applications.

The new 9- and 10-speed units under development will be used across each carmaker's range of cars, SUVs, trucks and crossovers. Like other multi-speed units, the new designs seek to maximize economy while delivering the kind of performance that buyers now demand.

Ten speeds really will mark Ford and GM out from the competition though, with more gears than any other manufacturer is currently working on. Transmission firm ZF recently announced it is working on a nine-speed auto, initially expected in to debut with Land Rover.

As emission and fuel consumption regulations tighten, transmissions with seven to ten gears are increasingly common. Modern technology makes their operation almost imperceptible to most drivers, yet the plethora of ratios enables the engine to work within its most efficient range more often.

By co-developing the transmissions, both companies are set to save hundreds of millions of dollars in development costs. Both will also benefit from economies of scale, with as much parts commonality between manufacturers as possible.

Only the software settings will differ, allowing each carmaker to tailor the transmission's behavior to suit the car engine it's matched with.

The agreement should also help both companies get a jump on competitors, as the combined resources of Ford and GM can be applied to speed the new gearboxes to market.

According to The Detroit News, we could see the new transmissions in the next three years.

It isn't clear which vehicles will benefit from the new units, but each company will announce specification details and vehicle applications closer to launch.

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