DETROIT – Acura strongly hints at its new ’15 TLX sedan with a prototype unveiled today at the 2014 North American International Auto Show.

The TLX, on sale midyear, replaces the 5-year-old TSX and TL sedans in Acura’s U.S. lineup.

The two models have been some of the brand's strongest sellers in the U.S., but sales of both fell sharply last year, with the TSX down 39.4% from 2012 and the TL down 27.6%, WardsAuto data shows.

While Acura isn’t offering many specifics of the TLX, it does confirm two all-new transmissions for the brand. An 8-speed dual-clutch transmission will be in models equipped with a 2.4L direct-injected I-4 engine, while a 9-speed automatic is to be paired to the same 3.5L DI V-6 engine powering the larger RLX sedan. However, the RLX mates the 3.5L engine with a 6-speed automatic.

Acura says the new 8-speed DCT in the TLX “takes full advantage of the 2.4L’s broad power band, delivering incredibly quick and smooth gear changes (and) expertly matching engine revs on downshifts.” The 9-speed automatic has closely spaced gear ratios and a wide overall ratio range for good fuel economy.

Acura is promising the 2.4L and 3.5L TLX will have fuel economy near the top of the midsize-luxury class, but cites no numbers.

The TLX also uses the RLX’s 4-wheel steering technology, Precision-All-Wheel Steer, and Acura’s next-generation Super-Handling All-Wheel Drive technology with torque vectoring.

Four driver-selectable modes will be available in the TLX: Econ, Normal, Sport and Sport+, which vary throttle response; SH-AWD and P-AWS logic control; and transmission shift-mapping, depending on the mode setting.

The prototype TLX is shorter than the current TL sedan but maintains that car’s wheelbase length and its class-leading interior volume.

The prototype wears Acura’s Jewel Eye LED headlights and has 20-in. 5-spoke, aluminum-alloy wheels. It is painted in Acura Athletic Red Pearl.

The TLX will be built at Honda’s Marysville, OH, plant, home to the current TL, and was designed and developed in both Los Angeles and Raymond, OH.

WardsAuto data shows TSX sales hit a record 38,035 units in 2006, while the TL’s high point was 78,218 in 2005.

cschweinsberg@wardsauto.com