Ford AOD transmission
| AOD | |
|---|---|
| Overview | |
| Manufacturer | Ford Motor Company |
| Also called | AODE 4R70W/4R70E 4R75W/4R75E |
| Production | 1980–2014 |
| Body and chassis | |
| Class | 4-speed longitudinal automatic transmission |
| Related | Ford FMX |
| Chronology | |
| Predecessor |
C4 C5 Ford FMX |
| Successor | 6R |
The AOD (automatic overdrive) is a four-speed automatic transmission with overdrive. Introduced in 1980, it was Ford's first four-speed automatic overdrive transmission. The gearset design is based on the Ford "X" automatic transmissions used during the 1950s, 60s, and 70s. 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. The new transmission was built around the Ravigneaux planetary gearset of the "X" transmissions. Where many transmissions had a fourth gear added on as an afterthought, Ford's new transmission was designed with a fourth gear integrated into the gearset. Because it was based on the "X" transmissions, its gear ratios from 1-3 were the same with the fourth being .67:1. The transmission featured a split-torque application for third gear as well as a lockup in the torque converter. The XT-LOD was initially abandoned in 1966 but design began again in 1974 as a result of rising gas prices. The project was shelved with a design that lacked a dampener in the torque converter but after the project was revisited a dampener ultimately made its way into the final design. The transmission was introduced when Ford started to downsize its full size line in 1979. Initially called XT-LOD (Extension Lock-Up Overdrive) its name was changed when revisited in 1974 to FIOD (Ford Integrated Overdrive) and then to its final name in 1979, the Ford AOD transmission.[3]
Applications:
The AOD was redesigned with electronic controls in 1992, becoming the AODE. It was mainly intended for the new Modular V8 at first, but it was also adapted to the old AOD bell-housing for vehicles still powered by OHV engines. While the AOD, AODE and early 4R70W share some basic components like oil pans, gear sets (AODs and AODE can be retrofit with 4R70W gear sets), most of the internals are not interchangeable because the 4R70W and AODE use electronic solenoids to shift instead of conventional hydraulics. The transmissions are not interchangeable either, as the AOD only uses a throttle valve cable for operation. The AODE and 4R70W's shift points are controlled by the Powertrain Control Module (PCM) also sometimes referred to as the Electronic Engine Control (EEC).
Applications:
A revised version of the AODE was released in 1993 with the Lincoln Mark VIII. Compared to the AODE, it has lower 1st and 2nd gear ratios for better take-off acceleration and was designed for better gearset strength. On vehicles powered by a 5.4 L V8, a stronger gearset is used than in normal duty 4R70Ws. In 1998, due to durability concerns, the intermediate one-way roller clutch was replaced with a mechanical diode providing extra holding capacity and longer service.
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