Chevrolet 1977 10 Series, Repair Manual, Page: 173 / 468

BRAKES 5-7
in the front housing.
3. Assemble the power piston group to the rear housing
by pressing the tube of the prim ary piston through the rear
housing bearing. Press down until the housing divider seats
in the rear housing and the prim ary power piston bottom s
against the housing.
4. Hold the rear housing assembly (with m ounting studs
up) over the front housing (make sure th at the piston rod
retainer does not dislodge from the secondary power piston
during this operation). Position the rear housing so that when
the tangs on the edge of the front housing are locked in the
slots on the edge of the rear housing, the scribe m arks on the
top of the housings will be in line.
5. Lower the rear housing assembly onto the front
housing. The power piston spring m ust seat in the depression
in the face of the secondary power piston. Check that the bead
on the O.D. of the secondary diaphragm is positioned
between the edges of the housings.
6. Assemble front and rear housings as follows:
a.
Straight Mounting Bracket
- Place Spanner
W rench J-9504 over studs on rear housing, and attach with
nuts and w ashers-draw nuts down tight to eliminate bending
or damaging of studs.
b.
Tilt Mounting Bracket (Chevelle)
- Secure
Spanner W rench J-9504 to bracket with three bolts and nuts.
D raw nuts down tight to eliminate damage to bracket.
c.
Tilt Mounting Bracket Except Chevelle -
Position Tool J-22893 inside tilted m ounting bracket. Place
Spanner W rench J-9504 on top of J-22893 and tighten nuts
and washers to bolts provided, securing Spanner W rench.
d. Press down on spanner wrench and twist rear housing
clockwise in relation to front housing until fully locked.
NOTE:
If unit is not easily locked, hold housings
together and apply vacuum to check valve in front
housing. D o not put pressure on power piston extension.
7. Remove Tool J-9504 and, if used, Tool J-22893 from
the rear housing.
8. Place the silencer in the closed end of the power head
boot. Push the boot retainer over the boot. Stretch the boot
over the push rod and over the flange in the center of the rear
housing.
9. Remove the power head assembly from Holding
F ixture J-22805 and remove Fixture J-22805 from the vise.
Fig. 5 -1 4 A ~ G a g in g P iston Rod
Gaging
1. Place the power head assembly in a padded vise (front
housing up).
Do not clamp tight.
2. Insert the master cylinder piston rod, flat end first,
into the piston rod retainer.
3. Press down on the master cylinder piston rod (w ith
approximately a 40-50 pound load) to be sure it is properly
seated.
4. Remove the front housing seal to assure th at no
vacuum is in the power head while gaging.
5. Place Gage J-22647 over the piston rod in a position
which will allow the gage to be slipped to the left or right
w ithout contacting the studs (fig. 5-14A).
6. The center section of the gage has two levels. The
piston rod should always contact the longer section (lower
level) of the gage. The piston rod should
never
contact the
shorter section (higher level) of the gage. Move gage from side
to side to check piston rod height.
7. Any variation beyond these two limits m ust be
compensated for by obtaining the service adjustable piston
rod and adjusting the self locking screw to meet gaging
specifications.
8. Wipe a thin film of silicone lubricant on the I.D . of
the front housing seal and position seal in the depression in
the housing.