ok, even thought this is an excursion, it's a 6.8L V10, tied to a 4R100 trans, 4x4.

symptoms : when i would put it in Drive it would stumble, hesitate, and shut down (engine cuts off). restart truck, and OD "OFF" light flashes. same symptoms occur till around 20mph, they they are sperattic but truck down not cut off. when pulling up to a stop light, the symptoms would repeat themselves about every other stop. no CEL, no codes even with light flashing. FINALLY got the CEL to throw a code P0720 according to the nearest autozone when the light came on.

trouble shooting so far :
- read on another forum where corroded battery cables were the cause of trouble codes to include the P0720 plus many others.
*** cleaned batt terminals (even thought they weren't that dirty to start with).......SAME PROBLEM
- read again where there was a problem with the speed censor on the rear diff.
*** took rear diff censor out, had some little shavings, nothing major, reinstalled censor, then tested voltage at plug with key ON-- 4.5Volts, tested the plug with engine running 5.0Volts, tested plug with engine at 2000rpm (cruising speed) 5.2Volts. not sure if this is all that is needed, but those are the numbers i came up with.
- read where a crazy thing happened to another guy where they replaced ALL speed censors, replaced PCM, replaced trans filter, and came down to the ALTERNATOR was bad.........
*** tried this last..... reset codes......unplugged the 3 prong plug on the alternator and test drove for a few minutes........ no blinking OD light, no CEL, no codes after 30min of driving... truck performs like it has in the past.

**** on another note i checked wires, plugs, and as much as the harness as i could for faulty worn wires, and i found nothing that was damaged.

NOW is there something i'm missing....... can / IS the alternator the cause of all this issue with the P0720 code being thrown, and terrible driving conditions? Is the voltage at the censors to low, or is that normal? Can i safely drive the truck for a couple days with that plug unplugged till i can get a new/reman Alternator??

thanks for any other input yall might have.

 

here is the thread i found with the Alternator being the problem.
https://www.ford-trucks.com/forums/6...ode-p0720.html

here's another one (post #9)
4r100 falling out of gear - Ford Powerstroke Diesel Forum

i think this is what i'll be researching tomorrow. everything seems to point toward that Alternator......