GMC 1976 ZEO 6083 Maintenance Manual page 250

Figure 38-Positioning Secondary Power Piston
the primary piston unscrews from the secondary
piston . If this happens, continue to turn the pri-
mary support plate counterclockwise. Tabs
("stops") on the primary support plate will tem-
porarily lock the primary support plate to the
primary power piston and permit continued
counterclockwise rotation to unscrew the pri-
mary power piston from the secondary power
piston .
13 . Remove the housing divider from the second-
Figure 39-Unlocking Power Piston
BRAKES 5- 3 1
Figure 40-Removing Secondary Diaphragm
ary power piston . Remove the secondary power pis-
ton bearing from the housing divider.
14. The secondary power piston should still be
positioned on Tool J-23101 . Fold back secondary
diaphragm from O.D . of secondary support plate.
Grip the edges of the support plate and rotate clock-
wise to unlock the secondary support plate from the
secondary power piston . (figure 40).
15 . Remove the secondary diaphragm from the
secondary support plate.
Figure 41-Removing Reaction Piston