2012 Ford E-350 5.4L motor with 4R75W trans.

Idles all day long with no issues, start driving and trans is stuck in 1st or 2nd gear. Will drive in 1st or 2nd forever with no codes thrown, but the second I manually shift to 1st gear a wrench shows up in dash indicating limp mode. This is when I get a P0731, and that is defined as a Gear 1 Incorrect Ratio. I ASSUME that the transmission is stuck in 2nd gear and when I shift to 1st manually the PCM thinks it should be in 1st but transmission is in 2nd causing the P0731 code and limp mode???

I also have drivability issues that are odd. After limp mode is detected the Van acts as if I have cruise control set at 20 mph. With foot off accelerator the motor will rev to 2000 rpm and accelerate the van as if cruise control is active. This happens for about 5 seconds and than rpm will drop to about 1300 and still accelerate van until I push on brakes to slow vehicle, then van will idle normal and not act as if cruise control is on.

I thinking shifting solenoids, or input/output sensor issues????
Maybe the Shift on the Fly sensor for accelerator pedal is screwy and causing transmission to act up???
Maybe throttle body electronics???

I have 165,000 miles on transmission with 2 fluid exchanges and filters in that timeframe. Well I did another pan and filter swap after this started happening so technically 3 filters and 2 fluid exchanges and 1 pan only fluid exchange in 165,000 miles.

Suggestions?