Автоматические трансмиссии Ford AOD, 4R70W/E и 4R75W/E: эволюция и модификации.

The AOD (automatic overdrive) is a four speed automatic transmission, with the 4th gear as 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.

First: 2.47:1
Second: 1.47:1
Third: 1.00:1
Overdrive: 0.67:1
Reverse: 2.00:1

In 2003, Ford revised the 4R70W transmission to include: A stronger ring gear that has 24 lugs (as opposed to 6) for the output shaft sensor (OSS) to read from, a revised torque converter, a revised front pump assembly, and a vehicle speed sensor (VSS) that complements the OSS to improve shift quality and efficiency. These improvements allowed the 4R75W to handle more power while being more efficient and economical. While not used on all 2003 model year vehicles, the 4R75W/E transmissions eventually replaced the 4R70W/E. Newer transmissions that are referred to as 4R70E or 4R75E have modifications that complement Ford's switching to throttle by wire. The PCM was given a more powerful microprocessor and Ford added a turbine speed sensor to the transmission. This allows the PCM to know the speed of the input shaft after the torque converter, which is used in combination with crankshaft speed to detect the amount of slipping going on in the torque converter. This information provides PCM with the basis for fully electronic shift scheduling, which limits "hunting", fine tunes shift speed, and feel. It lets the PCM know what the torque will be in the next gear so it can choose the shift points based on the vehicle's projected performance in the next gear. 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.

The most practical modification for the 4R70W is the J mod. 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. While these modifications can be done to the 4R75W transmission, the results are not as dramatic, as some of the details of the J Mod (bigger holes in the separator plate and gasket) were done to the transmission in its design. These modifications are specified by one of the Ford engineers who designed the transmission. It offers faster engagement, quicker shifting, smoother operation, and increased service life. All parts can be bought at Ford dealers for less than $60, including the fluid. A 20,000+ GVW cooler is highly recommended for all vehicles. Breakdown of the transmission fluid often results in "converter shudder" (it feels like driving over rumble strips) where converter tries to maintain a steady slip rate during lock up, but alternates between slipping and grabbing. Frequent fluid changes, especially when used for towing, are the single best method to prevent shudder. A shudder occurs because the torque converter never fully enters "lock up" and ends up bouncing in and out of lock up to slip. This causes the engine to flare up and then down again as the clutch cannot hold back the power of the engine.