GMC 1976 ZEO 6083 Maintenance Manual page 255

5- 3 6 BRAKES
the housing center hole fits into the groove of the
primary power piston bearing. The thin lip of the
bearing will protrude to the outside of the housing.
(figure 50)
37 . Coat the I.D . of the primary power piston
bearing with a thin film of lubricant.
38 . Assemble the power piston assembly to the
rear shell by pressing the tube of the primary power
piston through the rear housing bearing. Press down
until the housing divider seats in the rear shell and
the primary power piston bottoms against the shell.
39 . Mount Tool J-23456 in vise and position rear
shell in tool .
40 . Place piston rod retainer plate on the end of
the power piston and install power piston return
spring .
41 . Lower front shell over rear shell and position
bar on front shell with bearing.
42 . Tighten down on front shell and fit the tangs
in the appropriate slots on the rear shell.
43 . Rotate the bar clockwise into the locked posi-
tion and remove power head from Tool J-23456.
44 . Place the filter in the power head boot .
Stretch the boot over the push rod and over the
flange of the rear housing and install boot retainer .
45 . Place the power head assembly in a vise with
GAGE -J23337
REMOVE RUBBER REACTION DISC, PISTON ROD RETAINER & AIR VALVE SPRING FOR GAGING
(REACTION PISTON TOO SNORT) (REACTION PISTON TOO LONG)
AIR VALVE-PUSH ROD ASSEMBLY
Figure 51-Gauging Piston Rod
the front shell facing up . Insert the master cylinder
piston rod, flat end first, into the piston rod retainer.
46 . Press down on the master cylinder piston rod
to be sure it is properly seated .
NOTE : To assure that no vacuum is in the power
head while gauging, front housing seal must not
be installed at this time .
47 . Place gauge J-23337 over the piston rod in a
position which will allow the gauge to be moved to
the left or right without contacting the studs. (Figure
51)
48 . Position gauge over piston rod. The adjust-
ment is correct if the lower step contacts the piston
rod and the upper step clears the piston rod.
49 . If the push rod is not within specifications
and the push rod does not have an adjusting screw,
a new service adjustable push rod must be installed
and adjusted to specification . If the push rod being
checked has an adjusting screw, adjust the push rod
to specification .
50 . Wipe a thin film of lubricant on the I .D . of
the front housing seal and position seal in the depres-
sion in the housing.
51 . Position the master cylinder assembly on the
front housing. Install the locknuts on the studs and
torque to 28 ft . lbs.
52 . Install power unit into vehicle.
CORRECT
INCORRECT
A-1775