6T70 and 6T75 FWD transmissions

The Hydra-Matic 6T70 and 6T75 six-speed automatics are advanced transmissions with clutch-to-clutch shift operation for front- and all-wheel drive vehicles. The transmissions are based on a common design, with the 6T75 rated for higher torque capacity. The 6T70 debuts on the Saturn Aura and on a Pontiac G6 model; the 6T75 will be offered on the Saturn Outlook

The 6T70/75’s clutch-to-clutch operation and 6.04:1 overall ratio help the transmission deliver both performance and fuel economy, enabling up to 7 percent improved performance and up to 4 percent improved fuel economy when compared with current front-wheel drive four-speed automatics. Both transmissions use a very high numerical 4.48:1 first gear, which helps deliver exceptional launch feel, and a 0.74:1 overdrive sixth gear, which reduces engine rpms at high speeds, thereby reducing engine noise and vibrations. Fifth gear is 1:1 direct drive.

With its wide ratio and strong capacity, the 6T70/75 has the capability to transfer more torque to the drive wheels, particularly in all-wheel drive applications. It also helps vehicles, such as crossovers like the Outlook, to feel even livelier at lower speeds, particularly at launch or when pulling away from a stoplight.

The 6T70/75 offers the capability of driver shift control (DSC), which allows the driver to use tap-up/tap-down shifting to select the desired gear for specific road conditions, such as driving up a steep hill. A sophisticated transmission electro-hydraulic control module (TEHCM) is mounted inside the 6T70 and 6T75, reducing vehicle complexity. Similar to the control system used in the six-speed Hydra-Matic rear-wheel drive transmissions, the TEHCM offers improved quality through its hard-wired connections. The unit is located entirely within the transmission and operates while bathed in transmission fluid. Locating the controller internally facilitates the modular design and assembly strategy while also shielding the unit from the outside environment.

The 6T70/75 was co-developed with Ford Motor Co. Co-development of the transmission allowed it to reach production in less time and enabled each company to reduce development costs by as much as 50 percent. A common on-axis design and many common components are shared between GM and Ford Motor Co. The controls, calibrations and operation of the transmissions are unique to each company.