Car Will Not Start problems of the 2007 Nissan Xterra

The first time I noticed something wrong with the transmission, the vehicle would make a large vibrating sound at random times. This would keep getting worse until I had to bring it to a shop, overall just about a week. I was told the transmission and radiator fluids were mixing and that I needed a fluid flush a long with a new radiator. About 6 months later, my car just wouldn't start one morning. I take it to the shop again, hoping it is just a minor fix this time. This time there is something wrong with the transmission and computer system. Luckily I wasn't driving when this happened, otherwise who knows what damage it would have caused to the car or to me.

I was driving my car and it shifted into 4 wheel drive at a red light with no prompting. The car then was immediately pulled over and turned off. The car would not start following it being turned off. It was then towed to a mechanic shop where they discovered that the radiator had leaked fluid into the transmission, causing the coolant to mix with the transmission fluid and completely disabling the car.