| Manufacturer | Ford Motor Company |
|---|---|
| Also called | AODE AOD-EW/4R70W |
| Production | 1980–present |
| Predecessor | Various |
| Successor | 6R |
| Class | 4-speed longitudinal automatic transmission |
| Related | Ford C6 transmission AODE |
The AOD (for automatic overdrive) is a four-speed automatic transmission with overdrive. Introduced in 1980, it was Ford's first four-speed automatic overdrive transmission. The design is based on the same gearset as the 1960s and 1970s. The AOD replaced the majority of Ford's older transmissions, including the C4 and C6.
Applications:
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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 and AODE/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. 4R70W stands for 4 gears, Rearwheeldrive, 70 stands for the 4th gear ratio, and Wide gear ratio. It has lower 1st and 2nd gear ratios for better take-off acceleration and improved 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.
While there is speculation that the 70 can be multiplied by 10 to indicate the ft-lbs of torque this transmission is capable of handling including torque converter multiplication, (i.e. 700 ft-lbs of torque), there is no reliable source indicating this. In fact a Ford document stated that the 2003 "Expedition's 4R70W transmission is rated to handle up to 506 foot-pounds of torque, which provides a large performance cushion beyond the peak torque rating of Expedition's largest available engine." http://media.ford.com/products/presskit_display.cfm?vehicle_id=548&press_subsection_id=423&make_id=92 . It is more plausible that the number indicates the torque handling capability in N-m, as 506 ft-lbs converts to 686 N-m which could be rounded to 700 N-m. The "70" may also refer to the transmission's torque capacity after torque converter multiplication which occurs at low rpm's when the torque converter is more "elastic".
The gear ratios are: 1st: 2.84 :1 2nd: 1.55 :1 3rd: 1.00 :1 4th: 0.70 :1 Rev: 2.23 :1
Applications:
Many improvements have been made to the 4R70W since 1993, the most significant was the use of a "Mechanical Diode" beginning with the 1998 models. Newer transmissions are referred to as 4R70E, 4R75W or 4R75E to differentiate them from previous models. The 4R75E/W has greater torque capacity than previous models.
The most practical modification for the 4R70W is the J-mod. It involves modifying the valve body separator plate and gaskets and changing out some accumulator springs and removing others to alter the shift timing of the transmission. It encompasses modifications 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" (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. 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.
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