For about the last six month travelling between 60 75 miles per hour my Expeditions rpms wood jump from about 2000 to 3000 momentarily like the car was going from over dive to normal back and fourth. I then reached and disengaged the over drive and the Expedition ran real smooth I have replaced the crankshaft sensor, the computer. Expedition has 313000 miles any ideal what the problem could be. Thanks Rod

 

Sounds like an internal transmission issue. A solenoid or torque converter issue. I would have a good transmission shop examine it. With 313k miles, you might be looking at an overhaul. I doubt a fluid/filter service will help at this point.

 

An overhaul could be in your future,.
Certain conditions need to be met for the trans to go into overdrive and if any one of the inputs is intermittent, which could be a bad/loose connection or malfunctioning sensor, the trans responds to that fault. Might be a good idea to have the vehicle checked for any codes and go from there.

 

I have changed the transmission fluid and filter it didnt help. But on the flip side I travelled two hundred miles one way back two hundred miles with no issues at 75 to 80 miles per hour.it doesn't happen all the time. Thats what I find strange. When I took it out of overdrive it ran just fine without using the overdrive.

 

At no time did the engine light ever come on. Its been hard to diagnose, could a throttle position sensor be the problem?

 

At no time did the engine light ever come on. Its been hard to diagnose, could a throttle position sensor be the problem?

 

That will work for now but expect to use more fuel on the highway.

 

I would rather find the problem I am a one owner have had this vehicle since I bought new in 2000. Will it hurt anything if I don't use the over drive? Thanks for your help with this matter this Expedition has been a very dependable car.

 

Not using the O/D will not hurt anything. If you want it functional, I would consult a transmission shop. There is not much you will be able to do. You got a lot of miles accrued and likely will be looking at an overhaul.

 

There are sections/components inside the trans that need to function for overdrive to remain selected..
Sometimes, you might be able to see some of them with the fluid out and trans pan removed, but you need to know where to look..
Don't know if you want to go through removing the pan again and checking, especially with a lot of miles on the trans.
Vehicle condition and "sentimental value" will have a lot to do with your decision..