A/T - E40D No Forward Engagement In O/D, 4-3 Flare Up
TECHNICAL BULLETIN # 291TRANSMISSION: E4OD
SUBJECT:
No forward engagement in O/D select mode, 4-3 flare
APPLICATION: Ford Truck
DATE: Jan 1995
No Forward Engagement in the O/D Select Mode, 4-3 Flare
These symptoms are usually caused by a worn or broken O/D Sprag.
In the O/D select mode, the coast clutch is released and all input torque is transmitted through the O/D sprag. When the transmission shifts to overdrive the O/D sprag over-runs.
In the O/D cancel mode, the coast clutch is applied and overrides the O/D sprag.
Ford has updated the O/D sprag with a roller clutch kit which retrofits all E4OD transmissions (Ford part number F5TZ-7A089A). This kit includes the inner and outer races, the roller clutch and a new snap-ring (Figure 1).
The roller clutch assembly is similar to the earlier sprag. When installed correctly, the inner race freewheels counter clockwise (Figure 2).
A large contributing factor of the O/D sprag failure is that every time the vehicle is started, the computer resets to the O/D select mode. Because of this, most driving is done without the coast clutch applied.
Heavy loads, full throttle starts and other types of abusive driving put a great deal of stress on the O/D sprag.
To remove some of this stress, block the coast clutch shift valve toward the retainer. To do this, remove the coast clutch shift valve assembly. Remove one and one half coils from the spring (Figure 3). Reinstall the assembly with the spring first then the valve, and then the retainer (Figure 4).
With the coast clutch shift valve blocked in this position, the coast clutch will be applied in first second and third gear in both the O/D cancel and O/D select mode. The 3-4 shift valve will release the coast clutch in overdrive to allow the sprag to over-run.