Hi Guys, I have a 1999 5.4L 2WD with a few issues. Wanted to reach out for your thoughts on the following:

Issues/Background:
1) Overdrive light will begin flashing around 60-70MPH - does not flash at lower speeds. OD light stops blinking upon restart and only reappears around the same speeds.
2) At approximately 45-50MPH transmission seems to up and down shift every 2 seconds; RPMs "slightly" go up and down at the same time.
3) Scanner (non-ford specific) pulls the following codes (P0741) and (P0136)
4) I tried cleaning the O2 sensor in question regarding (P0136) but it did not clear code
5) I did reset codes via scanner - but they all came back after driving ~10miles
6) Next, I disconnected battery - but all came back again after driving ~10miles
7) Not sure what to check with regards to P0741, but I do know that transmission fluid is not low and does not appear dirty

Any thoughts on what to check next? Many thanks in advance for any feedback!