2000 ford explorer 5.0 shifting problems

[HyperSin]

I did a 2000 ford explorer 5.0 swap into a ranger if thats important information, if not disregard.. so the transmission (4r70w) has a werid shift problem ive never encountered before, it will downshift perfectly fine but at crusing speeds (4th gear) and will randomly downshift to 3rd gear then back to 4th randomly and just today (7-16-2025 it went all the way back to second gear then third then fourth, could it be the shift solenoids, pcu is not throwing any codes yet

 

[C420sailor]

if you can get your hands on Forscan, you can run live data on it to see if the PCM is commanding the downshifts or not. That will help you narrow down what’s going on.

If the PCM is, it could be based on bad input sensor data, like a failing throttle position sensor or output shaft speed sensor. If the PCM isn’t, then it’s likely a hydraulic or mechanical issue that could be caused by a servo, valve body, etc.

 

[Turdle]

High throttle position sensor output will command downshift. If the tps ever got wet, replace it.

 

[410Fortune]

You need to monitor live data

So this is a conversion, has it ever been correct or is this something that’s happening now that the truck is running?



Trans codes are sometimes continuous memory codes and you have to go into the scan portion of your code reader and look for manufacture specific codes


Did you have the pan off the transmission ever?

The transmission and pcm came from the same donor?