Differential Unit problems of the 2005 Nissan Pathfinder

During the month of December 2012 I had my Nissan truck serviced. The diagnostic test recommended to replace rear differential fluid, replace cabin air filter, replace windshield wiper blades, air filter, perform engine coolant exchange , transmission fluid exchange, power steering system fluid exchange, perform brake system fluid exchange, and fuel injection . I also had to replace the catalytic converter, which was done by Nissan. I had all of these services performed by the Nissan automotive department. On February 28 2013, my service engine soon light comes on along with sensor light indicating a door is open. However, no doors were open. I take the truck back to Nissan, and they tell me the transmission is about to go out!!!! how is this possible? I have always taken my truck to Nissan to perform the service . I am outraged!!!! all of the service needed has always been performed by Nissan. Please help!!!!.

While backing out of a parking space, I heard a loud "clang" which sounded like it came from the engine compartment or under the front of the car. It sounded like a metal rod hit another piece of metal. As I was already out of my space, I proceeded forward, but my car lacked power. I was finally able to gain enough power to move forward, but something was obviously wrong. I was able to get my car to the dealer, avoiding the highway for fear of getting hit by someone while my car had very little responsiveness. The dealer inspected the car and claimed to be surprised of the failure, which was that transmission fluid had leaked into the radiator, and coolant into the transmission. The dealer quoted me $7000 to fix this issue. After calling around and finding an aamco dealer who explained to me this well known issue, I was quoted a price of "only" $3800 to fix it. The problem, as described by the mechanic, was a faulty design where the transmission fluid travels through the radiator with some sort of valve box between them and the heat differential between the coolant and transmission fluid necessarily causes the valve box to decay causing the 2 fluids to mix. The result is a completely ruined radiator, completely ruined valve box, and if not treated early, a completely ruined transmission. Obviously, if I am driving my children on vacation and we're coming down a mountain when the transmission fails, this could be very tragic! now I am out a car, forced to obtain a rental car, and still need to correctly fix my own car. What's more, if I use the same components that Nissan has designed, I will only be setting myself up for future problems. I looked online to see if anyone else had this problem and was amazed to find so many people with the same issue, describing in detail pretty much what the aamco mechanic told me. I find it hard to believe that the folks at Nissan had never heard of it. It is obviously a faulty design and Nissan needs correct it.