2001 Hyundai Santa Fe Won't shift into gear

I keep the oil changed regularly and have changed the automatic transmission fluid three times. While I was accelerating slowly the car seemed to have shifted out of gear. This happened without warning, or any type of grinding, popping noises of any type. This happened so suddenly and without warning the engine started to race and I thought I had by accident moved it into neutral. The only gears that appear to be working are park and neutral. All other do not, drive, 1st gear and reverse all fail with no response and the engine will race when you give it gas. I immediately checked the fluid level (engine running and normal operating temperature) and the fluid was red and clear with no indication of excessive wear. The check engine light is not on.