My 97 explorer sport does not shift into overdrive. What is the problem?

Need to know a couple of things first. Is the service engine soon light on? If so, did it come on with the overdrive problem, or was it already on? Also does the O/D light flash at all. And do you have the "O/D off" button on the shifter handle or is it a separate switch in the dash? Once I know these things, I may be able to help.

NO lights are on or blinking. The O/D button is on the shiffter.
Thanks for your time.

The first thing that needs to be verified is that the over drive solenoid is working. To do this you need to have a Ford scan tool hooked up to the vehicle. I'm sure that not everyone has a Ford scan tool. You may have to go to the dealer. The over drive solenoid needs to be actuated by the scanner, and there should be an audible click heard from the transmission pan area. If the solenoid is working then the most likely cause is worn clutches for overdrive or intermediate clutches. That usually consists of a trans overhaul, as the overdrive clutches are deep into the trans, and it doesn't make sense to just replace those clutches if you have to take the rest out anyway. If the solenoid is not working then possible causes are the solenoid, internal or external wiring, or PCM (powertrain control module). Either way some diagnostics has to be done in order to find the problem. No quik fix or common problem that I know of. If you send me the VIN I can check for service bulletins or service messages through Ford. My email is [email protected].