Fast shifting

I have a 95 Century that shifts from low to overdrive way to fast. Also it will not downshift until complete stop. It may do this for 2 weeks then start shifting perfect for a couple of weeks before acting up again. Any suggestions?

Welcome to AF!!

Have the car scanned with a trans capable scanner. They can check the shift points for you. To see if there is a problem but based on your description it sounds like you may have a PCM issue that is causing it to shift too fast.

Your car uses a vacuum modulator to control part throttle shifts. Look for trans fluid in the vacuum supply line to it and if present, replace the modulator. The modulator is located on the front of the transmission case near where the trans cooler lines connect to it (between the trans and radiator). I will be about 4-5" in diameter with a single bolt holding it in and a single vacuum line running to it.

thanks