The AOD replaced many of Ford's older transmissions, such as the C4, C5, and light duty applications of the FMX.
In 1962 Ford began working on a new type of automatic transmission that would emphasize fuel economy and driveability.
It was primarily intended for the new Modular V8 at first, but it was also adapted to the old AOD bellhousing for vehicles still powered by pushrod engines.
Unlike the AOD-E, Reverse, 1st, and 2nd gear ratios in the 4R70-W are numerically higher, giving the transmission a better mechanical advantage and, in turn, better take-off acceleration, better passing acceleration, slightly lower fuel consumption, and designed for better gearset strength; the 4th gear ratio in the 4R70-W is up 0.70:1 from 0.67:1.
In 1998, the intermediate one-way roller clutch was replaced with a mechanical diode due to durability concerns, thus providing extra holding capacity and longer service.
[citation needed] The PCM was given a more powerful microprocessor and Ford added a turbine speed sensor to the transmission.
Coupled with the electronic throttle strategy, the transmission computes the output torque required to maintain the vehicle speed and chooses the correct gear and converter state accordingly.
It involves modifying the valve body separator plate and gaskets as well as changing or removing accumulator springs to alter the shift timing of the transmission.
It offers faster engagement, quicker shifting, smoother operation, and increased service life.