GMC 1990 Light Truck Repair Manual page 349

8. Primary Piston Bearing
9. Rear H ousing
10. Front H ou sing
11. Return Spring
38. Power Piston
Group
Figure 26—Booster Inner Components
• Check that the beads on the secondary dia­
phragm (20) are seated evenly around the
complete circumference.
16. New diaphragm retainer (15) and seat 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. Primary piston bearing (8) into the rear housing (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).
Piston Rod
12 .
(Gaged)
13. Reaction
Retainer
14. Power Head
Silencer
15. Diaphragm
F-05823
Retainer
Primary Diaphragm
16.
17. Primary Support Plate
18. Secondary Piston Bearing
19. Housing Divider
20 Secondary Diaphragm
.
Secondary Support Plate
21
.
Power Piston Assem bly
41.
* Use J 37839 If not within limits, obtain a ser-
vice adiusta,3,e Piston rocl-
BRAKES 5-13
Figure 27—Power Piston Group
F-05893