Driving to work yesterday morning. The first 10 km were uneventful. Then rolling down a long, steep hill. My foot basically off the throttle. Normally my 91 F-250 will coast at 700rpm during this maneuver. Halfway down the hill the rpm jumped to 1100 (speed about 80 km/h). It seemed to have gone out of overdrive. During the rest of the the drive to work, the transmission would shift at significantly higher speeds than normal. This applied to all gears, from first to overdrive.
Driving home in the afternoon, the same story.
But this morning, everything functioned normally.
Does anyone have an explaination?

 

I do not know much on this but with my parents 4-runner (sorry not ford) that happens whenever the extra power button turned on. Mabe it was accidentally turned on then off (if you have one).

 

Your truck has an E4OD tranny. Two common problems that would cause the symtoms you are describing are related to either your engine tach sensor or your vehicle speed sensor.

Are your RPM gauge and speedometer working perfectly or are the needles sometimes jumping around or not showing properly or comming in late?

The electronic controller on the tranny uses the above sensor inputs for shift control. A intermittent sensor problem would cause erratic shifting.

 

Here's another thought. When coasting down the hill the truck is going to cool off. If there is some problem with a sensor, thermostat, pump advance or ?? it might be thinking it's cold and set the advance on the pump which could be sticking a bit for whatever reason.
Sensors can operate within the specified range but be on the low or high side of operating voltage and not set a trouble code. I've had many sensors over the years that did that very thing. It sure makes it a pain to trouble shoot.

 

Since the RPM and speedometer both work as they should, I too have suspected a faulty sensor (or two). But a temporary problem is a pain to locate. I was hoping someone had experienced the same thing, and could guide me directly to the source of the trouble.

 

There are several key sensors that can give you trouble intermittently. The good part is the truck will store these codes as continues codes in the continues memory which can be retrieved with a scanner. Just because your OD trouble light is not on does not guarantee that their have been no errror codes stored in continues memory.

The simplest things to check and probably replace just to eliminate them are sensors 1 thru 3 listed below: (These three sensors are all common trouble makers and addressing them can solve probably 70% of all tranny issues)

1.0 Engine Tach Sender: ($70-$90)
2.0 Vehicle Speed Sender: ($90 -$100)
3.0 Throttle Position Sender (TPS): ($60-$100) (Note, needs to be calibrated after installation)
4.0 A somewhat more expensive sensor is the MLPS (Manual Position Sensor) ($200) and in my experience this unit should be only replaced if you got a code to support a failure of the MLPS) Also, Ford changed the connector style in and around 92' so changing over the wiring harness to the new connector style is a real pain. Takes lots of patience and time.

5.0 If none of the above works you next bet would be to pull the oil pan. The condition of the oil and any metal in the pan will tell a quick tale as to the mechanical condition of your E4OD. Metal in the pan is bad news.

6.0 Assuming everything looks good oil wise and you have gone thru all the sensors above the next thing would be to replace the solenoid pack. (Again there should be some Code to support a failure (such as shift errors) Purchase cost for a new solenoid pack is about $400-$500 and along with the oil and new filter this job will cost you about $600 - $700 in parts if you do it yourself. Note, the solenoid pack also contains thermostat circuitry so if you are getting overheating codes without actually overheating then replacing the pack might fix that.

7.0 If you have done all the above, have good power, ground, and proper wiring connections, and a functional controller, the tranny should shift properly; except perhaps the dreaded CODE 62 (3-4 shift error). Typically a Code 62 is a death sentence to the Torque Converter and may even further point you to a total tranny teardown and rebuilt if the root cause of the torque converter is a failure on the TC lock-up shift valve located in or around the oil pump I believe. Given the cost to change a Torque Converter ($800-900 installed) vs. re-gasketing the whole tranny ($1600 to $1,800) you need to seriously think about whether it is worth while to pull the tranny twice (i.e. spent another $600 to $800) if it turns out that the TC lock shift valve was the real problem for the lock not working. Don't run on the new TC if the valve is not good as it will just destroy the new TC in a very short time.

As a last note, the very first thing to do is make sure your tranny oil level is where it is supposed to be. (Cost $0.00)

 

Thank you, Hamberger, for your extensive answer. I realize I have a lot to learn. For now, I will do nothing, but observe closely the behaviour of my transmission, hoping the problem may have been related to weather/temperature/humidity. If it occurs again I will follow your advise, troubleshooting and replacing, starting at the least expensive end of the scale.

 

All that I have read about these E4OD trannys is beginning to get me down! Mine started acting up a day ago. It started shifting hard from 1st to 2nd, and hard into 3rd. From 3rd to OD it was still nice and smooth. Seemed like the less accelerator, harder shift. But now tonight it went back to normal, smooth shifting. Any imput would be apprieciated.

Phish555
94 F350 CC turbo diesel.

 

When you were going down the hill did you rest your foot on the brake pedal, if so you caused the torque convertor lock up to release and increased the rpm 200-300 rpm.

 

IF you put any pressure on the brake pedal the torque convertor will unlock other wise when you came to a stop the engine would stall, the torque convertor clutch acts just like a clutch in a manual trans.. all trans calibratiions in any ford work this way! Now it is possable that the calibration in this truck is set up to stay locked on decels after a period of time to control vehicle speed on down hill runs.

 

I only occasionally applied the brakes to control the speed.