Brake Antilock Wheel Speed Sensor problems of the 2001 Chevrolet C/k 3500

Abs pulsates on left front wheel when applied (a noise eminates from the left front wheel). Dealer replaced right front hub and left low speed brake sensor. Brakes still pulsated on left front side. Returned to dealer and was told now the left hub needs replacing. (did not have replaced. ) pulsation in brake system had not stopped after the two earlier repairs. Have spent over $1000. 00 for these repairs and do not feel the gm experts know what they are doing. Want the problem resolved, but don't want to spend another $1000. 00 only to find out that the problem still exists. Is this problem a sign of a future safety issue? I haul a large fith wheel camper and fear brake failure after perusing the complaints on the gm abs system.