Q: Transmission grinds, clunks, & whines on interstate

I was driving on the interstate and I heard a noise like grinding metal. At first, I thought I had a flat tire, so I pulled over but couldn't find anything wrong with any of the tires. After entering back onto the highway, the sound returned. Not only the grinding noise, but there was a 2nd high-pitched whining sound coming from the transmission. That was followed by a clunking that kept occurring and then something blew! My car began to slow down even though I was trying to accelerate. I pulled to the edge of the highway and turned the car off. Then turned it back on again. When shifting from Park into Drive, it did so fluidly and also from Drive into Park. However, when I started trying to move forward, it started making that clunking noise about 2 times per second. No warning lights came on and I am fairly sure that the transmission fluid is in good shape. What is your diagnosis for all of this and what will fix it?