I have a 2009 5 GT with 39000+ miles on it. I am in San Diego CA. Last weekend coming from a trip from Phoenix, AZ I noticed that the transmission slipped after leaving a restaurant. No problems on the highway and at fast speeds. Brought it to dealership and they kept it for a day. They said they couldnt find any issues, no codes, but they did a transmission fluid change because the fluid was dark. After leaving the dealership, transmission seemed ok and fixed. But in the evening it slipped again shortly after leaving home. \

What could this be? So frustrating since I bought the car last year exactly one year 11/26/11 and had no problems since then. Car is certified and under powertrain warranty until 2016. Bumper to bumper was only for a year though! Such a hassle to bring it back to the dealership who cant find the problem...and their service department is closed on the weekends so I have to do it on a work day.