Hello everyone, new to this site,could anyone give me some insight to what might be wrong with my car...............it shifts harsh only after it's good and warm/hot,i have changed the filter and oil and it still does it.When it's cold it shifts as smooth as butter,city or town driving seem to bring on the harsh shifting.

General Motors uses a computer strategy called Shift Adaptives.I will try and inform without boring.The vehicle computer,PCM,monitors all shifts,all the time,every time.It does this using tenths of seconds as the measuring stick.When a shift,any of the 3 shifts (4 gears) repeatedly takes TOO long to complete,generally .7,.8,.9 tenths of a second or longer,and i say repeatedly,because the computer has to see this abnormality several times.When the computer sees this,it tries to overcome the long shift/abnormailty by electrically sending a signal to a variable force motor,that mechanically,raises hydraulic line pressure inside the transmission.This is what you are feeling,the computer raising line pressure,trying to compensate,and everything gets harsher.Eventually,likely,the computer will set a P1811 code "Maximum Adapt and Long Shift".