I have a 05 LLY Silverado, first it started with the rear left caliper sticking. So I replaced it and eventually it stuck again. Then a few days later I was pulling my car trailer (having to use the brakes a bit harder) the front left stuck. Now almost everytime I drive it the front right sticks. Ive replaced the master cylinder with a used one and still have the problem. Oh yeah and when it does stick, the pedal gets rock hard. I dont wanna keep throwing parts at it till I find a definite fix. Thank you!