The E4OD transmission system was introduced in 1989 and used in both light and heavy duty applications. The E4OD was the successor to the C6 transmission and was Ford’s first electronically controlled automatic transmission. It comes equipped with four forward speeds as well as electronic shift controls to replace the hydraulic governor control of its predecessor. The E4OD transmission can be found in applications such as the Bronco, the Expedition, and the F-Series:
- 1990–1996 Ford Bronco
- 1989–1998 Ford E-Series
- 1997–1998 Ford Expedition
- 1989–1998 Ford F-Series
- 1993–1995 SVT Lightning
Ford’s E4OD automatic transmission was designed from many improvements, changes, and upgrades to the earlier C6 system. Improvements include a higher contact ratio in planetary gear sets, an improved hydraulic pump, and upgraded coast clutch. The E4OD also featured the addition of an overdrive gear set, which greatly improved fuel efficiency over the C6’s direct drive top gear. The E4OD also introduced the concept of electronic shift controls, replacing hydraulic pressure regulation and shift functions with electric shift solenoids. In this transmission, shifts would be commanded electronically by means of the EEC-IV on-board control processor.
Ford called the transmission control processor the ‘Electronic Control Assembly’, or ECA. The unit could also be interpreted as a modern transmission control module, or TCM. The ECA controls transmission shift timing, regulates transmission line pressure, controls the torque converter lockup sequence, and provides certain diagnostics of the transmission. In gasoline applications, the ECA controls electronic functions for both the engine and transmission. In diesel applications, the ECA instead acts as a stand-alone controller for the transmission and does not play a major role in engine function.
The E4OD was eventually replaced by the 4R100, which was Ford’s transition to an alternative name for their drivetrain products, since the transmission is similar to, but not interchangeable with the E4OD. The 4R100 included changes, upgrades, and improvements necessary for Ford’s automatic transmission platform to compete with the F-Series diesel program.
A flashing “OD” light on the shift lever of an E4OD indicates that the ECA has detected a transmission problem and is alerting you to take the vehicle in for diagnostics, service, and/or repair. The E4OD was improved multiple times over the course of its existence – when overhauling the E4OD, so you should consult with your transmission expert to ensure you receive any and all updated components that may provide favorable reliability and durability.