Driveshaft problems of the 2004 Ford Explorer Sport

Started in 7/2007 had vibrations in drive train, Ford stated it was the drive shaft. Ford replaced the drive shaft with a high-performance balanced one. Vibration stopped. In 10/2007 the explorer was slipping during acceleration, and slamming into gear. Overdrive light would be blinking on and off. This time they had said that they had to rebuild the transmission due to a bad oriface. Later I found out they only replaced the valve body at 24072 miles. I asked about the lag time between pressing the accelerator and actually moving and was told that this was the way the vehicle drives due to no cables for the throttle it was electronic and there might be a computer update at a later date. It hesitates upon acceleration just had to learn and accept it. Vehicle had been fine until about Feb 2011 when it started to slam into gear again, after scheduling for 90000 mile check told Ford to please check this out. I was told that this time it was the servos for the overdrive and that the transmission had to be rebuilt or a new one purchased for about $3500. They stated it was a design problem, that the servo rods were made of steel and the trans casing was made of cast aluminum, hard metal slamming into soft metal wearing the orifice to an egg shape causing pressure loss. The new design trans has been corrected. Upon checking on a Ford explorer forum on the web found out that this is an issue with the 2002-2005 5r55s and 5r55w transmissions due to the design flaws. If it's a design flaw they should correct it and not charge $3500 when you already purchased there product.