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

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.

by in Bremerton, WA on January 16, 2013
2 answers
ANSWER by on January 16, 2013
Warped brake drum or rotor comes to my mind.
ANSWER by on January 16, 2013
brake drums out of round as stated