As I was driving to work this morning, I got to a stoplight, as I was accelerating I felt a fairly large bang. I let off the gas and drove carefully, it did it again so I pulled off to the shoulder. I turned it off then back on and tried putting it into drive, it kicked itself back into park and the transmission fault message popped up. Tried again and it did the same thing. Every time it did this the P N and D all flashed off then back on. Even while I was just sitting there they flashed every once in a while. Any ideas? Am I in for a large bill?