Brake Problem - '99 Silhouette

I have a '99 Olds Silhouette. While traveling under 5 mph, applying the brakes causes the van to come to a jerking stop. The jerking seems to be originating from the rear. It is as if the ABS system is working at the slow speed, yet the ABS light does not come on. Therefore, I took out any fuse that was labled ABS. This did not stop the problem. I looked at the brakes and I don't see anything obviously wrong. Does this mean that it would not be a speed sensor and not related to the ABS system? If so, what else could be causing this?