High RPM stuck in low gear and getting low speed on highways

Hi Dave: Thanks for your advice. Unfortunately, the warranty is no longer valid. Remember: the car works fine at low speed. It only seems to slip into stronger gear when it is running at fast speed at highways. I do not travel much; therefore, I could not detect the problem earlier. What could be the cause for that problem? Some people have said it might be due to weak fuel pump; others say that probably the speed sensors are worn out. Are you saying the cause might be in the high speed gears? I wish I could have a clearer view of the source of the problem before spending more money into it. Thanks for some help...

Whereas I cannot say anything for certain without being there to see your vehicle, I can say that what you are experiencing is probably a slipping overdrive band or something to that effect. Or, you could have a shift solenoid not shifting to the higher gear. Tough thing to figure out without feeling the nuances of the shifting and feeling what the transmission is actually doing. Better yet, being able to monitor or command shifting with a diagnostic tool would be a big help in diagnosis too. I can definitely say your fuel pump is not to blame. I do not suspect speed sensors have any part of this issue as well. Again, this is where a diagnostic tool monitoring the systems is important to see what the components (sensors, solenoids, etc) are doing. Good luck.

Thanks again! I will have the vehicle returned to the mechanic for tests with diagnostic tool or else. As soon as I have this problem fixed I will give you some feedback. Happy new year!