1994 idi 7.3. Auto 4x4.
finally had some time to fix things. Calipers, new rad, ripped out rotten rear fuel tank and gonna order a new one. A bigger one.

Anyway, sometimes while driving down the highway, it seems to downshift or fall out of gear. Sometimes I could mash the throttle or let off and ease back into it and back to normal.
other than that it holds and shifts at wide open throttle fine and shifts good. So I don't think anything mechanically wrong with the tranny.

The throttle position sensor on the side of the fuel pump I checked with a fluke meter and watched the voltage curve for a few minutes as I worked the throttle back and forth. No dead spots or high spots in the curve, it appears the sensor is working.

So that leaves maybe a bad ground to that sensor or transmission, or something I'm not thinking of. Just wondering if anyone else had the same thing happen and have an idea where to check.

There's also the slight possibility that the sensor could be bad and just read fine because the truck wasn't running and driving thus no vibration? I mean it does drive fine 99% of the time so 🤷 maybe that sensor is bad and only does this randomly with the right vibration from driving I'm not sure.

 

does you O/D light work ?
does it flash when it falls out of gear ?

 

I have seen this before. It won't set a code.

The problem is a bad MLPS (Manual Lever Position Sensor.) It's on the driver's side of the trans where the shift cable attaches. Just replace it. Testing usually won't show the issue.

 

No od light flashing.

 

Ok I will look if I can see where it is and see if I can find one.