Thanks for the insight Liftdoctor. As a matter of fact I am servicing one now that has this problem. I installed new shoes and actuating arms, and drivers(the small trapazoid shaped inserts in the middle of the shoes), and emeried the drum, which is in excellent condition. I agree about the nearness of the hyd. breather (have seen this also), but my recent repairs have eliminated this.I will try a new backing plate, and cam and will post the results.This seems a logical answer.