2006 Ford Explorer XLT intermittent engine rev

Engine revs excessively when I press accelerator to shift between 2 and 3 gear. It acts like the transmission is having problem “up shifting”. However I had the transmission checked thoroughly and all checks out OK. New fluid, no leaks, compression good, bands good, no debris in housing etc. This engine rev also occurs while stopped at stop lights for no reason. (no acceleration, etc) I also notice the fan behind the radiator running at high speeds when engine is in idle mode. Fan revs and then slows and then revs again. Don’t know if this is related) Engine rev is not related to running the AC. It happens if AC is on or off. The fan rev and the engine rev are not the same sound or symptom.The vehicle runs fine when I first drive it on 40 mile trip to work in the AM. As the day goes on and the vehicle is driven more then the engine rev problem shows up. (again on an intermittent frequency). Question. Could a dirty fuel filter cause this engine rev. Question. What might be some things to check out to find and resolve this problem?

Your not going to like this answer but what you are identifying is the same problem I had on my 2002. Yes, the transmission are supposedly different but it sure sounds the same. Have you noticed any idiot lights - 4X4 low, or 4X4 high or OD lights. If you have those, you are headed for a transmission rebuild. Good luck!