HEY--my 2000 durango seems like it doesnt want to stop,i have recently replaced all the shoes so i know its not that.Sometimes you will feel like it doesnt want to stop and the wheels will lock up and skid on the road as if you hit the brakes hard when you really didnt.I noticed that the brake fluid was low on the back of the master cylinder near the booster,so i topped that off,but still the same---does it sound like it could be the master cylinder or maybe the booster?---thanks for any help