Toyota Develops 6-Speed Gearbox

Transmission development at Toyota Motor Corp. is shifting into a higher gear – the sixth gear.

The auto maker has developed a 6-speed automatic transmission for rear-wheel-drive application that first will be seen in the Lexus LS 430 flagship sedan and likely will be offered in other higher-end Lexus models as well.

The A761E transmission, which Toyota unveiled here at the Society of Automotive Engineers World Congress, stands apart from the burgeoning 6-speed competition in several regards, including performance and fuel economy; size and weight; shift feel and quietness.

Fuel economy has been improved over Toyota’s conventional 5-speed automatic, thanks to a wide gear range with close gear steps and a reduction in parasitic losses. These developments make for an improvement in fuel economy of 8.7% off-the-line performance and 14% improvement at a cruising speed of 62 mph (100 km/h) when compared with today’s 5-speed.

Toyota claims its new transmission is the world’s smallest and lightest, due to an “ultra-flat” torque converter, compact solenoid and optimum valve body design and packaging.

The 6-speed makes for quieter running because engine speed is reduced at high-speed cruising, and Toyota says it also has been able to reduce the amount of noise produced by the gears, themselves.

Toyota isn’t the only one adding speeds to its automatic transmissions. Two new 6-speed automatics developed by AISIN also were unveiled here. Mercedes-Benz already offers a new 7-speed, dubbed “7G-Tronic,” that emphasizes performance as well as comfort and fuel economy.

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