I waited until you got your answers from others here with more knowledge on the subject before commenting.
Your broken axle is terrible but it could have been tragic. I too was lucky in when I discovered mine just before it broke in 1977. I kept hearing a noise in the rear whenever I turned right. My Pontiac dealer showed me the old axle when they worked on it. Its diameter, at the location of the bearing, was about half its normal. The bearing failed and was cutting through the axle shaft. Your looks like a different failure cause.
