99 neon tranny problems

I have a 99 neon dohc, the car sat for 1 1/2yrs i changed trans fluid and filter cause trans is shifting hard and down shifting prematurly even after the change sometimes it shifts ok but always goes back to the hard up shifts and down shift early, im thinking its a sensor, can anyone help on this issue?

I dont know much about tranny problems, but...both the shifting hard and the premature downshifting (while accelerating) could be caused by a misadjustment of the Throttle Pressure Control Cable, that runs from the throttle body to the top of the transmission. To quote the service manual, "If the setting is too short,shifts may be delayed and part throttle downshifts may be very sensitive". It doesnt seem easy to describe how to make the adjustment though, lacking the diagram that is in the manual. On my car I expect I would have to take out the battery and battery tray in order to be able to see this location. The adjustment is done at that lower end of the cable, not up by the throttle body. You could also check to see that the Throttle Pressue Control Cable is resting inside the grove around the rim of the throttle wheel.

thanks for the comment, i guess i failed to mention that when it downshifts on its own is like when im getting of the freeway and even when im coming to a stop light, its downshifting way to early