1997 Ford Explorer OD light blinking and shifting hard

My Explorer is having some issues. Engine runs fine but when I start to drive it, the Overdrive light starts to blink and the transmission seems to shift hard and fast. It also sounds like its not hitting the top gear. After driving it a little, It wont go at all. Meaning no drive or reverse or even park for that matter. I took it to autozone and hooked up their computer under than dash and it says there is no erorrs. Any ideas what this could be?