I was driving up a steep hill in the middle of a busy shopping district when this problem occurred. I hear a weird sound like a elephant roar/lawn mower for about 10 seconds coming from somewhere in the back of my car. I look at my rear view mirror and all I see is black. Black smoke, or exhaust, steam, I don't know, but it's flowing out of muffler and basically filling up the street with black car exhaust. It's really embarrassing when it happens too because the sidewalks were filled with shoppers and other people. They ALL stopped and stared. And then the coughing. I swear they must have all started coughing as if I gave them bronchitis or something. About half of the 300 + people started to "boo" at me. All this and I'm still climbing up this hill in my car. The smoke keeps coming out at a good steady pace and continued to until I got home and shut the car off. Right after the car turns off, the muffler and the attached pipe fell to the floor of my garage making a loud "thud" noise. The whole thing a very embarrassing experience. No mechanic I've had look at it knows what to do. And they all say to get rid of the car. But I don't want to because I won't get any money in return. The car was $2,000 new in 1970. There no trade in value in that.