I have a 2002 XLE with less than 40k miles. I took it to 2 different dealers and they claim they cannot replicate the problem, but it still happens. If I am cruising around 50 MPH (give or take a few MPH) and the car needs to upshift or downshift, it will shake or buck a little. It doesn't do it always, but frequently. 2 times it did it so violantly that the entire car and passengers shook. Most of the times, only the driver can feel it and it doesn't last long. I found a bulletin and took it to one of dealers and showed it to him and even then I had to argue with him. They then said they found and installed a software upgrade for the transmission. My wife tells me it still does it on occasion. Any suggestions?