[gmtech1]

Sounds like maybe you are have a low speed ABS activation. If so, you can try and clean the front wheel speed sensors, and inspect the grease in the hub assy when the sensor is out. If its rusty looking the hub needs replaced. There is a recall out for some of these and much info in this forum if you seach " low speed ABS activation" in the suburban forum.
In the end you will probably end up replacing the front hubs.