GMC 1976 ZEO 6083 Maintenance Manual page 249

5- 30
BRAKES
AIR VALVE
PUSH ROD
ASSEMBLY
FLOATING
CONTROL
VALVE
PUSH ROD
LIMITER
WASHER
FILTER
FLOATING CONTROL
VALVE RETA I NER ~
SECONDARY
POWE R P I STON -----4`
BEARING
HOUSING
DIVIDER
PR (MARY POWER
PRIMARY SUPPORT HEAD
DIAPHRAGM PLATE SILENCER
DIAPHRAGM
SUPPORT
RING
PRIMARY POWER
P I STON
RETAINER
PLATE
SECONDARY
POWER P I STON
SECONDARY
SUPPORT
PLATE
SECONDARY
DIAPHRAGM
REACTION BUMPER
AIR VALVE SPRING
REACTION
DISC
REACTION
PISTON
P I STON ROD
RETAINER
Figure 37-Exploded
2 . Remove master cylinder attaching nuts and
remove master cylinder from front housing.
3 . Remove front housing seal and master cylinder
piston push rod.
4. Install Tandem Diaphragm Separating Tool
J-23456 as shown in Figure 36 .
5. With cylinder clamped slightly, rotate bar
counterclockwise and unlock shells .
6. Back off hold down sufficiently to remove
front shell, return spring retainer plate and piston
rod retainer .
7 . Remove assembly from tool and remove tool
from vise .
8 . Remove the dust boot retainer and boot from
the rear housing and push rod. Remove the felt si-
lencer from inside the boot .
View of Power Piston
9. Remove the power piston assembly from the
rear shell and remove the primary power piston bear-
ing from the center opening of the rear shell.
10 . Lift the bead on the outside diameter of the
secondary diaphragm and remove the support ring .
(figure 37)
11 . Mount Piston Unlocking Tool, J-23101, in a
vise with wide jaws up . Position the secondary power
piston so that the two radial slots in the piston fit
over the jaws of the tool . (figure 38)
12 . Fold back primary diaphragm from the out-
side diameter of the primary support plate. Grip the
edge of the support plate and rotate counterclock
wise to unscrew the primary power piston from the
secondary power piston . (figure 39)
NOTE : It is possible that the primary support
plate will unlock from the primary piston before