Automatic Transmission problems of the 1999 Plymouth Neon

I was driving & I heard a "clunk" & a "boom" & then the car shut itself off. After getting out of the car, I realized that there was a puddle of transmission fluid underneath the car. I had a mechanic look at it - there's a hole in the gear box where the transmission shot the park gear right out of the box - he said it had to be a defect. [there's only 16,000 miles on the car] I called Chrysler regarding this [& was treated extremely rudely by their customer service department, might I add. ] & they refuse to do anything about this. They told me that because the car is no longer under warantee, the defect is not their problem.