I recently had a used automatic tranny installed in my 2000 Plymouth Neon. It works fine for the first 10 - 15 miles and then it seems to downshift by itself while doing 55 mph. I am holding the gas pedal steady and it's like it shifts into 1st gear. The rpms go way up and the engine keeps accelerating. I have to put the gear shift in 2nd to get where I'm going. It has plenty of fluid. Does it just need something adjusted or is it a bad tranny? The warranty on the tranny is good til Dec. 15.

 

Someone with more knowledge on neons might chime in with some better info but my brothers neon was having weird shifting issues and I replaced the cam shaft sensor and it seemed to fix it. Could aldo be a tv cable that needs ajustment no idea where to do that on theses. Its ussualy on the braket the throttle cable goes to.