I was inspecting a 3030 MGM brake chamber on a bus and found something that didn't look right. With no brakes applied, the push rod was sticking up farther than it should. Then I pulled the dust cap off the top of the brake chamber. Come to find that it didn't look right. So we changed out the piggyback. To do so you first apply the service brakes. Then take a vis-grip plier and clamp it on the push rod, close to the face of the brake chamber. You can leave the service brake part of the chamber and the slack adjuster in place. There is a clamp that holds the two halves of the brake chamber together. Taking off the camp, witch allows you to take the piggyback (maxi brake part) off. Them you should bleed out the air in the lines, by applying the maxi brake. Now you can take off the two air lines and now the piggyback is totally free. To install the new piggyback just revers the process.
rear right side rear left side
(broken brake chamber) (still good)