So first of all my 03 maxima has 175k miles on her and has had a slight issue with shifting hard usually only when cold so i never push the car this is my daily driver i have my other project cars so this one doesnt really get beat on at all, here is my story, just the other day i went to pass a car going about 50mph had the throttle at about 3/4 way down nothing crazy the car downshifted from 4th to 2nd gear and shifted real quick into 3rd gear passed the guy went up to about 75mph nothing shocking there but now the car refuses to shift into 4th/od under any circumstances slow driving or even hard driving, i have used the stick to manually shift and when i put in 4th/od nothing changes the same as 3rd gear. I went to use cruise control at about 60mph and the car will stay at about 3.5k rpm then drop to 2k rpm and then shoot back up to 4k rpm real quick and it will do this until i take cruise control off. I took the battery out for the weekend went for a drive still the same issue, im thinking it might be a TCM issue but wanted to hear anyone elses opinions, anything helps at this point.

 

I would suspect the transmission solenoid more so than TCM but it could be either. Have you checked for any (pending) codes? Also, a drain&fill, repeated two or three times, may help.

 

I had similar problem with my 3rd gen- it would engage/disengage on hwy driving me nuts. The culprit was 'transmission position sensor', I forgot the exact name. It was a rotational sliding contact type sensor with contacts which got dirty over years. Its faulty output was confusing TCM causing all the trouble. Cleaning the sensor cured the problem for years up until I sold the car, it never came back. The car was also failing simple tests- when leaving shifter in 2nd it was supposed to shift between 1 and 2nd but it would never leave 1st or something of that sort. The sensor was located in front of transmission, right on the same axle of the lever the shifter cable was attached to: cable would change lever position and the sensor would tell TCM its position.

 

Did you use any certain kind of cleaner for the sensor?

 

It's called Park Neutral Position switch, take a look at AT267 of 2003 FSM, it shows its location. It has misleading name as it tells TCM more than just about Park or N positions. I cleaned it with Deoxit D5 and put electrical grease after but any cleaner should do, it was really dirty. I had to open it to get to the contacts.