Why did my used 94 ford Taurus stop working when i shifted it from overdrive to the second driving option?

I just bought a used 94 ford taurus and it was driving fine for a week or so, but on the way back home on a road trip I was curious to see what the other driving option was and shifted into it for a little bit. Nothing bad happened. It drove but i wasn't comfortable driving in it on the highway so I stopped and shifted back to overdrive. Then when I tried to accelerate on the highway the car wouldn't speed up and the engine made a funny noise. I eventually came to a crawling halt and had to pull over on the shoulder. Any ideas of what could be wrong with it, because it was working great until I shifted those gears.