Transmission Slip Out Of Gear problems of the 2003 Lincoln Aviator

I own a 2003 Lincoln Aviator, still under warranty. Since around November of 2004 I have been having transmission problems. The problem is the transmission will slip out of gear while driving at a steady speed, accelerating from a stop or slowing down and then accelerating. This is very hazardous when trying to merge onto a highway or turn into traffic and the vehicle will not accelerate. The problem exists in all gears, however, it does not do it all the time. It has continued to get worse. Each time the dealership has told me that they could not duplicate the problem. On April 15th 2005 as I was leaving my office parking lot the transmission started acting up. It was slipping out of gear in all gears. I immediately drove the vehicle to the Ford dealer. On the 21st of April almost a week after I dropped it off I was told again they could not duplicate the problem. On the same day, 21 April 05 I went to pick up my vehicle and the head mechanic had it out for a test drive. He stated upon return that the vehicle acted up. My vehicle stayed with the dealer for the next 15 days while they took apart the transmission, ordered parts, etc. A few days after I received the vehicle back the dealership called to see how the vehicle was running. I explained that it still didn’t feel right but I would continue driving it and note any problems I encounter. As of today, 23 may 05, the transmission does not always shift smoothly and I have had three occasions were the transmission took a very long time to shift from one gear to another. This to me is just a sign and the beginning of more problems. During the course of my many visits to the dealer I was informed that problems exist with my make of transmission, not only in the Aviator but with the explorer and the Mercury suv’s. What I don’t understand, if there is a problem with the transmission why hasn’t Ford/Lincoln acted on it and put out a bulletin or recall. Sincerely lori bell.