GMC 1989 Light Duty Truck, Repair Manual, Page: 331 / 998

BRAKES 5-13
8
.
9.
1 0
.
11
.
38.
P rim a ry P is to n B e aring
Rear H o u s in g
F ro n t H o u s in g
R eturn S p rin g
P ow er P isto n
G ro u p
F-05823
Figure 26— Booster Inner Components
• Check that the beads on the secondary dia­
phragm ( 20 ) are seated evenly around the
complete circum ference.
16. New d ia p h ra g m re ta in e r (15) and se at using
J 28458.
17. Silencer (14), reaction retainer (13) and piston rod
(
12
).
• Lubricate the inside and outside diameters of pri­
mary piston bearing (
8
) with silicone grease.
18. Prim ary piston b e a rin g (8) into the rear h o u s in g (9).
19. Power piston group (38) into the rear housing (9).
20. Return spring (11).
• Align the scribe marks on housings (9 and 10).
• Lock the front and rear housings using J 23456 (fig­
ure
21
).
• Stake the housing after locking. Stake two
tabs 180 degrees apart (figure 23).
• Do not stake a tab that has been previously
staked.
• Assembly can be aided by connecting a vac­
uum source to the booster.
• Lubricate the inside and outside diameters of the
grommet (4) and front housing seal (7) with a thin
layer of silicone grease.
21. Grommet (4) and vacuum check valve (3).
22. Front housing seal (7).
23. Silencer (2) and boot (1).
• Gage the piston rod (figure 24).
Figure 27— Power Piston Group
Use J 22647. If not within limits, obtain a ser­
vice adjustable piston rod.
12 .
13.
14.
15.
16.
17.
18.
19.
20
.
21
.
41.
R e ta in e r
P o w er Head
S ile n c e r
D ia p h ra g m
R e ta in e r
P rim a ry D ia p h ra g m
P rim a ry S u p p o rt Plate
S e c o n d a ry P is to n B e a rin g
H o u s in g D iv id e r
S e c o n d a ry D ia p h ra g m
S e c o n d a ry S u p p o rt Plate
P o w er P is to n A s s e m b ly
F-05893
P is to n Rod
(G aged)
R e a c tio n