2004 RAV4 transmission noise

I have noticed that my 2004 RAV4 makes a transmission noise that I hear mainly when I start and stop, but it does make the noise all the time. It sounds to me like a transmission that is low on fluid and I have taken it to the dealer and they have no idea and the toyota technicians have recomended replacing it with a new one but the mechanics at the dealer said that they drove a ladies new RAV4 with only 1800 miles on it and that it made the same noise. Does anyone else have this problem because if they all do it then I won't send it in but if not then I want it fixed asap. I would appreciate anyones input. The best way to test for the sound is to stop by a wall on the driver side with the window down and then start and stop, on mine the sound even changes gears with the transmission. They tried to tell me that it was a tire noise at first but then I took them for a ride and let them hear. Thanks for the input.

Any thought about using synthetic transmission fluid?
RH