1994 GMC Safari Q&A

1994 GMC Safari Question: What is causing a knocking sound when I apply the brakes?

The knocking sound only seem to be heard from under the back of my van whenever I slow down and come to a complete stop. There is no sound after I stop nor after I resume driving. Sometimes the knock is slow and and rapid. The sound is frequent. -
Answer 1
Warped brake drum or rotor comes to my mind. -
Answer 2
brake drums out of round as stated -