Since I have owned this vehicle I have experienced erratic shifting, primarily when driving in traffic, and when the vehicle is downshifting to 1st or 2nd gear. It has occasionally occurred when traveling on the highway during an upshift, but this is rare. I have also experienced lurching when stopped, or creeping forward in anticipation of a turn. I can occur at any time, and under any type of conditions, hot or cold. It also has a tendency to shift harshly when shifting from park to reverse or from reverse to drive. I have expressed my concerns with my dealer, and it appears they are aware of the problem, and have told me that GM is also aware of the issue, but they dismiss it by way of saying it is normal. I have had the transmission fluid changed at the regular interval, but this has not cured the problem. Finally, GM is well aware of this issue, and is subject to class action lawsuit regarding these transmissions, and other owners have stated that they too have experienced this shifting issue. My concern is that this will eventually lead to a failure of the transmission and the drive components i.e., drive shaft, pinon gear, differential housing, anything connected to the transmission. If this failure occurs at highway speeds, a possible loss of control and crash could occur.