Specifications for an E40D Transmission

The E40D has a first gear of 2.71 to 1, second gear ratio of 1.54 to 1, third gear ratio of 1.00 to 1 and fourth gear ratio of 0.71 to 1.

The E40D was Ford's first electronically controlled automatic in light trucks. According to "Popular Mechanics," the E40D receives commands from the EEC-IV on-board engine control computer, "which processes input from engine, transmission and the vehicle itself to determine the best shift points for performance and consistent shift feel."

According to Ford, factors in determining the shift points of the transmission include the transmission temperature, engine speed and altitude. Ford claimed 25 percent better fuel economy in the 1991 F-150 two-wheel-drive pickup with the E40D transmission versus the 1990 F-150 with the older C-6 transmission.

E-series vans and F-series trucks with the E40D from model years 1989 through 1993 have a shifter pattern of P-R-N-OD-2-1. These models also have an overdrive cancel switch.

In 1994, Ford introduced the 4R70W transmission, which uses the same shifter pattern, making it ineffective to examine the shifter to determine which transmission the vehicle has. All 4.2-liter and 4.6-liter, and some 5-liter, Ford engines use the newer 4R70W. Diesel vehicles and those with 4.9-, 5.4-, 5.8-, 6.8- and 7.5-liter engines have the E4OD.

For an alternate way to determine a truck's transmission, measure the transmission fluid pan. The E40D pan measures approximately 20 inches in overall length, whereas the 4R70W transmission has a length of about 15 inches.

Components you can replace with upgraded aftermarket parts include the computer, torque converter, sprags, clutch piston, front pump, sun gear, rear case bushings, pressure regulator, reverse boost valve and center support. You can also add auxiliary oil coolers to ensure greater reliability.