Hi Joe, your common is very problem on the 02 and earlier 4T65E transmissions. It often goes away when you shut the car off and then after you drive it a short while it starts shifting very firm or hard and you can sometimes here the trans pump whine. This is caused by a failing pressure control solenoid most of the time. The pcm tries to command trans line pressure one way or another and when it doesnt see what it wants it will max out the line pressure as a fail safe. Dropping the pan and changing the filter or taking it in for a flush is not going to fix the bad solenoid, though it may slightly soften up your shifts as new fluid has agents to keep shifts smooth that break down over time. I would get ahold of a scan tool or take it to a trans shop or someone knowledgeable and have them scan the car and watch the PCS Amps and also check for code P1811
