Chrysler Group LLC is pumping $300 million into its transmission manufacturing complex in Kokomo, IN, to accommodate production of a new 8-speed automatic gearbox starting in 2013.

The auto maker does not disclose which vehicles will benefit from the “highly fuel-efficient” transmission. But in today’s market, against a backdrop of looming mandates for fuel-economy improvement, 7/8-speed automatic transmissions are exclusive to rear-wheel-drive architectures.

Chrysler’s fullsize ’11 cars, which consists of the core-brand 300 and Dodge Charger which share a rear-wheel-drive platform, are getting a major overhaul.

And a statement released today by the auto maker does not preclude an 8-speed rollout before production begins at Kokomo.

“Chrysler Group has licensed the manufacturing rights from Friedrichshafen, Germany-based ZF Group to build the new eight-speed beginning in 2013,” the statement says. “Included in this agreement is the purchase of transmissions manufactured by ZF.”

The investment, which will fund the installation of equipment and tooling to upgrade the site’s transmission and casting facilities, while also securing 1,200 jobs, is the second to benefit Kokomo in less than a month.

Chrysler previously laid out $43 million to “support production of the (4-cyl.) World Engine and improve processes for the 62TE transmission program.”

The auto maker was similarly mum about the need to improve capacity for 6-speed automatic transmissions. However, Chrysler is the only Detroit OEM not to offer a 6-speed automatic transmission in midsize cars equipped with 4-cyl. engines.

As of model-year ’09, 7/8-speed automatics only could be found in imported luxury cars bearing the Infiniti, BMW, Mercedes-Benz, Porsche and Lexus brands, according to Ward’s data. Like-equipped vehicles accounted for just 9.4% of import cars sold in the U.S.

The technology was absent from all light trucks, as well as the domestic-vehicle population.

A ZF 8-speed transmission supplied to BMW AG for its V-12-powered 760i and 760iL flagship sedans boasts low friction losses and a taller gear ratio that help deliver a 6% gain in fuel economy.

“The new 8-speed automatic transmission will offer our customers refinement and comfort while achieving greater fuel economy and performance,” Paolo Ferrero, senior vice president-powertrain, says in a statement.

“We look forward to integrating the new transmission into future Chrysler Group products and welcome its contribution to a corporate fuel economy improvement of more than 25% by 2014.”