I have this same problem in my 05 grand prix and it is really annoying. It has a rotational squeak in park and neutral, and at very low speeds (pulling in and out of my driveway). When completely stopped with my foot on the break it sometimes screaches. Seems to go away with a tranny temp of about 140 degrees. I have taken it to two mechanics and two tranny specialists. No one can figure out the squeak. I have read several posts describing the same noise i am hearing but in different vehicles. No one seems to be able to help any of them either. Can ANYONE help???
