Those ECUs are kind of spendy for the diesels. I looked on line and if you send your unit in they will rebuild it for $650 and another source sells them for $850. I would want to know for sure before spending that kind of money. If I were a gambler I would bet that is what your trucks problem is but I don't bet with someone else's money. Since your truck hasn't thrown a CEL with fault codes that is another symptom in is in the ECU.

 

So for anyone looking at this and having the same issues with your truck as I did I finally found the problem. It was the alternator to begin with. It burned up my VP44 by causing a issue with the torque converter in the transmission and wouldn't find "home" so to speak and the motor kept revving between 50-150 rpm while driving. That $112 dollar part cost me over 3k by the time I found the issue after I was told it was the APPS, cam sensor etc etc. So if you have any of the same problems test out your alternator, after years of use it back feeds "noise" and that causes issues in the tranny and in the APPS. Hope this helps anyone looking for a similar problem.