Transmission stopped going into overdrive runs strong with overdrive off . switch it on and drive normal no issues other than won't shift into overdrive.drive it hard (as I normally do) overdrive light starts flashing and starts shifting hard from first to 2nd.thinking i need to to change filter and fluid but may need to do a lil upgrade with the trans pan off ,I've seen several post on solenoid or harness issues even valve body replacements what solenoids would this encompass and can I buy a full package from somewhere any and all help appreciated guys.

 

Solenoid 3(or C) is used for OD and also for 2nd gear
If you check for transmission codes(need a more expensive OBD reader for that) you will most likely get "incorrect 5th ratio", and maybe "solenoid C" code

2001 Ranger 4.0l will have the 5R55E(5 speed) transmission, same internally as the 4R55E(4 speed)
So where did the extra "gear" come from?

It comes from software in the computer
Like most transmissions, manual or auto, 1st gear will be a high ratio number, this is to get the weight of the vehicle, PLUS any load, moving from a standing start
Then 2nd gear will be almost 1 full ratio away from 1st, the 4R has these, 2.47(1st), 1.47(2nd), this means the engine needs to REV higher before shifting into 2nd, if not then when you shift to 2nd engine will bog down, RPMs will be too low and out of the power band of the engine
Other gear ratio changes are 0.5 or less, i.e. 3rd is 1.0, OD 0.75, so much less of an RPM difference

OverDrive is on the output shaft of an automatic, so it can technically be turned ON when any other "gear" is being used, kind of like a "gear splitter", or 2-speed rear axle
So Ford added software, to 2001 and up Ranger computers, that will turn on OD when in 1st and RPMs/speed are at correct point
So 2.47(1st) OD on = 1.87(faux 2nd), then shift to 1.47(now 3rd gear), so engine doesn't need to REV as high and has smoother shifting

And there in tells the tale of why I think you have an issue with solenoid C, the OD on/off solenoid
No OD of course
But also the now "hard shift" to 2nd, but its not actually 2nd, its hard shift to 3rd, because with no OD there is no 2nd in a 5R55E
Why its not working is something you will need to find out
The Transmission Codes should give you some info, but computer codes can only diagnose electrical issues NOT mechanical issues

 

Had a scan and it did come up with 5th ratio thnx gonna replace c and filter an fluid see what I get 🙏

 

Consider adjusting the Bands also while your under there.