So my 1991 F590F Super Duty (dana 80 5.13's with 10 lug, Duallies, 14mpg) with the 7.3 IDI non turbo and the famous E4OD which has only 82,500 miles on it now. As usual I have the same OD flashing light, it goes away daily once the engine eventually warms up. But I read somewhere that there is a sensor that doesn't let the torque converter fully engage until the engine reaches full temp. The name of that sensor escapes me. Couldn't this be one of the culprits that plagues the E4OD. I was thinking of changing this sensor. I got my fipl set to 1.0 at idle, checked, this, checked that, done a professional tranny flush.

 

Welcome to the foum.

I think you are asking about the TOT sensor.

TOT = transmission oil temperature (sensor)

It is soldered into the PC board of the solenoid body in the valve body. Not even sure if its possible to replace that unless you know what part to get from an electronics catalogue. Generally they don't go bad, but anything is possible.

Here is how it works.

The TOT sensor will be used to detect temperature by the PCM. Once the temperature passes 100F, the torque converter clutch will be allowed to engage if conditions are right. When its colder than 100F, it will not lock up at all but the torque converter will still work as a normal fluid coupling. This is the normal operation of the transmission.

What often happens with these E4ODs is the torque converter clutch will not lock up properly if the friction element get burned off, or the apply clutch piston develops cracks preventing enough fluid pressure to clamp on the friction element. Valve problems in the front pump can also cause a delayed engagement that is slow enough for the PCM to store a slip code.

Speedometer and tachometer have to work perfectly for for the E4OD to remane sane. Does the truck have cruise control and does it work? Having the truck scanned for codes could help narrow down the problem.

 

David, The truck does not come with a tach, but there is a tach sensor installed but the speedometer is always off by at least 10mph. No cruise control either. so if the speedometer says 60, I am really going about 50.