I have a 97 3500 with a BD exhaust brake, vacume operated - blue toped and probly 10 years old. The vacume pot is hanging part way on. I called BD and inquired if there was an internal spring inside, and they said no, that it used vacume to pull it off and on. I have the vacume system working corectly. Turn brake on and it goes full on. Turn brake off and it goes to mid tarvel. Vacume will not pull it up to the off position. I am going to remove the pot and take it apart. I wonder what i am going to find? Any clues ? BOB ALLER