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How Did the E40D Differ From Previous Transmissions?
While the E40D transmission was never used in automotive applications, its durable construction made it perfect for heavy-duty truck powertrains. The E40D would be manufactured by Ford from 1989 - 1998 model year and used in the Ford F-Series (‘89 - ‘98), Bronco (‘90 - ‘96), E-Series Vans (‘89 - 98), Expedition (‘97 - ‘98), and the SVT Lightning (‘93 - ‘95).
The previous C6 automatics were three-speed transmissions with a simple, Simpson planetary gearset and flexible Borg-Warner shift band. The shift points were controlled by a governor mechanism through hydraulic pumps. The E40D replaced the hydraulics with electronic shift controls while borrowing many C6 components. Ford had to enlarge the transmission to accommodate an additional planetary gear set for the new fourth forward gear. A new valve body was recreated.
The E40D had a lockup clutch in the torque converter, designed to improve fuel efficiency and power during highway cruising. While the V8s continued to get notoriously bad mpg ratings (the ‘89 F250 had an average of 12.8 mpg), Ford tried everything it could to bump the numbers higher.
The E40D had an aluminum exterior. But it was heavier than the C6 due to the added gear set. (The C6 was 175 lbs dry, but because the E40D weighed a hefty 270 lbs with the converter).
The transmission had a low gear ratio of 2.7:1, significantly better than the C6.
The Specifications of the E40D
The following contains specifications for the E40D
The Common Problems With the E40D
While the E40D is a widespread transmission for classic truck restorers, it is prone to some issues.
Faulty Torque Converter
Because the transmission was more extensive than its predecessor, the company needed ways to save production costs. The designers turned their attention to the torque converter, and instead of strengthening it for the new gearset, they continued to use many of the same components from the C6. Ford owners discovered the fragility of these OEM parts as lockup clutches burned up or froze.
As you can imagine, this frustrated many owners, who hated it when their trucks would stop running. This issue occurs with trucks with higher mileage, so often, the repair was not covered under warranty.
Solution: Many early torque converters require upgraded lockup clutches to ensure proper functionality. They failed to strengthen it for the new gearset, often connecting them to a separate solenoid with wires that often lost their connections. Since Ford
Leaking Valve Body
When Ford designed the E40D, one of the components that required a complete overhaul was the valve body (extra space was needed for the addition of the fourth gear and lockup clutch). Unfortunately, the factory-installed valve bodies were prone to leakage at specific stress points.
Customers found their trucks shifting poorly or utterly unresponsive due to line pressure issues with the pressure regulator valves.
The biggest issue for the valve body was that it was made of aluminum, which tended to warp under high heat. Since many of these problems occurred at low mileage, many owners felt discouraged that they had to bring their trucks into the shop after having just bought them.
Solution: Many aftermarket units are machined to completely seal the valve body. If you are restoring a classic truck with the OEM valve body, and find that the truck is shifting poorly, check for leaks underneath and replace the valve body with a newer unit.
Cracked/Broken Output Shaft
Since the E40D was a transmission with overdrive, the transmission was forced to endure extensive pressure during times. While the overdrive was helpful in saving fuel at higher speeds, it couldn’t hold up under towing pressure. Many owners found that the output shaft was taxed too much and could overheat, crack or fail.
The worst time to experience transmission failures is cruising down the highway with a camper or boat in tow. Truck owners were exasperated with Ford for the faulty design and let their voices be heard. (Some later units have strengthened shafts designed to mitigate this issue).
Solution: Many current output shafts are made to withstand more pressure than early models. The only solution is to replace the output shaft completely by rebuilding the transmission.
The Solenoid Block
The E40D was controlled by electronic inputs from the torque converter clutch solenoid block. This component was responsible for dictating the shift points of the truck. Unfortunately, the original unit was not weatherproof, allowing moisture to invade the unit. (As anyone knows, water and electricity do not mix). The lack of an effective seal against the elements created performance issues, as internal components (particularly range sensors) would cross-fire or short out completely. Owners found that some of the solenoids had faulty connections, which led to transmissions shifting in and out of gear or locking up.
Solution: Ford tweaked the solenoid block for most of the E40D production run, so by the time the transmission was ready to retire, they had designed a reliable unit. (The issue is that most classic trucks from this era don’t have the new blocks installed). Check the part number on the block to see when it was produced and replace it if there are issues.
Oil Pan Issues
The OEM oil pan was unusually small in volume on the E40D, which created issues leading to high operating temps. As the transmission was stressed, the higher temps would lead to burnout, component failure, or leakage. Many owners found that the transmission could not handle the strain of towing or heavy payloads in lower gear ratios.
Solution: Many classic restorers would change out the OEM oil pan for a deeper unit, which seemed to solve a host of issues. The deeper pan prevents a cracked case and is worth the trouble of replacing it.
Rollaway Risk
Some Ford truck owners found that their trucks would slip into reverse gear after shifting into park. (The transmission tended to slip in and out of gear when it wasn’t supposed to). Ford tried to rectify the issue, but many trucks slipped through the cracks and were never repaired. The problem did not present itself until the owner would put their truck in “park” and watch their truck roll away after they’d gotten out of it.
Solution: Since the issue does not present itself until the moment it happens, it can be hard to diagnose. There are many issues that can cause the problem, from faulty shift cables to linkage issues. This issue is challenging to trace down.
Is The E40D An Easy Transmission To Find Parts For?
While many trucks from this era are still working in fields like champs, parts for the E40D are becoming more scarce and rising in price. The transmission is not easy to rebuild, and most restorers would be better off purchasing a remanufactured tranny to install rather than attempting to tear the original apart. In addition, rebuilding the transmission without replacing the torque converter is just asking for problems down the line.
