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Honda's new 10-speed transaxle for front-drive vehicle applications is a packaging triumph. (Lindsay Brooke photo)

Honda’s new 10-speed is a slick shifter

Honda’s 2018 Odyssey offers room for eight passengers and its transaxle is packed with 10 forward gears. Developed in-house over a three-year period, the new automatic is the industry’s first production 10-speed for front-drive vehicles. It is being produced at the company’s Tallapoosa, GA, transmission plant.

Automotive Engineering was fortunate to speak with Tom Sladek, principal engineer at Honda R&D in Raymond, OH, about the new gearbox during the Odyssey’s media unveiling at the Detroit auto show. He said the transaxle’s input torque rating is 370 N·m (275 lb·ft) “with some degree of headroom designed in.” While Honda has yet to announce the SAE-rated torque of the Odyssey’s 3.5-L V6, it is expected to be greater than the 2017 engine’s 250 lb·ft (338 N·m). SAE peak horsepower of the 2018 engine is 280 hp—a 32-hp increase over this year’s output.

Interestingly, Honda is launching the new minivan with two available automatic transaxles—the ZF-sourced 9-speed and the new corporate 10-speed. The latter, equipped with standard stop-start, will initially go into the premium trim-level models. It is slated to proliferate steadily throughout the Honda and Acura ranges, replacing Honda’s 6-speed automatic for 3.5-L V6s. The new Odyssey is front-drive only.

The overall ratio spread of 10.1 compares with 9.81 for the ZF 9-speed used on the Honda Pilot/Acura MDX and TLX and a 6.03 spread on the factory 6-speed, a 66% increase. The 10-speed is overdriven in gears 7 through 10. Sladek promised “beautifully smooth” kick-downs for rapid acceleration because the transmission is designed for non-sequential skip-shifting—it is capable of downshifting from 10th to 6th gear or from 7th to 3rd instantaneously.

Optimized internal ratios in combination with “a continuing focus on reducing internal friction” help boost the Odyssey’s fuel economy by at least 6% over the 6-speed, he said. The wide ratio spread allows engine rpm to be reduced to 1,500 rpm at 62 mph (100 km/h), compared with 1,920 rpm on 6-speed vehicles. The spread of ratios (Sladek did not have gear-by-gear specifics at the show) enables a 14% improvement in highway passing acceleration and a lower first-gear ratio boosts off-the-line grunt. Redesigned electro-hydraulic controls and a revised solenoid design provide a 30% faster gear-change response time, he claimed.

After the 10-speed first appeared in October 2015 at a Honda technology demonstration event in Japan, the company’s patent filings for an 11-speed transmission surfaced online for a brief period. The 11-speeder incorporates three clutches, same as the new 10-speed which was Sladek’s focus in Detroit. He walked us through some details aided by a cutaway property in Honda’s auto show display. AE was actually second on the scene when the cutaway was wheeled in—a ZF engineer was already snapping photos when we arrived.

“Optimizing the overall package was one of our primary design goals,” Sladek noted. “Overall length is just under 15 in (375 mm)—about 1.7-in (45-mm) shorter than our existing 6-speed.” There are four planetary gearsets aligned with the crankshaft axis, along with the three clutches and three brakes. Sladek pointed to key design elements that contribute to the ultra-compact package: a new two-way clutch that replaces the forward/reverse mechanism’s one-way clutch and multi-disc brake; a smaller diameter and slimline torque converter; and a clever ring gear incorporating a row of teeth on its inner diameter that transfers torque to the differential.

The high-attenuation/low-inertia torque converter incorporates a three-stage vibration damper that was engineered and calibrated for the V6’s cylinder deactivation and stop-start systems, Sladek noted. An accumulator activates the 1st-gear clutch either rapidly or slowly, depending on operational inputs, to optimize the engine stop/restart sequence. Competitors and your reporter look forward to experiencing the slick-shifting 10-speed later this year.

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