Chevrolet 70 1969 Series, Shop Manual

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POWER BRAKE 5-6
and front housing. Scribe m arks on front diaphragm
housing and hydraulic cylinder body. Scribe m arks on
control valve housing and hydraulic cylinder body.
2. Rem ove m ounting bracket from hydraulic cylinder
body.
3. M ount unit in vise with vacuum cham ber up and vise
jaw s gripping the hydraulic cylinder body. Tighten
vise only enough to hold the unit; do not tighten vise
enough to distort the hydraulic cylinder body.
4. Remove clam p band and rear housing assembly.
5. Remove tube and nut assem bly from control valve.
6. Rem ove lock nut from end of push rod and remove
diaphragm and plate assembly, spacer and diaphragm
return spring.
C AU TIO N : O uter e d g e o f diaphragm plate is
very sh arp a n d can cause severe cut if not pro­
perly handled.
7. Remove two bolts which fasten front housing to hy­
draulic cylinder body. Rem ove front housing, rein­
forcem ent plate and gasket.
8. Rem ove snap ring from hydraulic cylinder body and
pull push rod, bushing and piston assembly out of
body as a unit.
9. Slide washer and bushing off push rod.
10. R em ove block vee from bushing.
11. Rem ove O-ring and spacer from push rod.
12. Rem ove snap ring from piston and separate push
rod, piston and hydraulic cylinder valve.
13. Rem ove valve insert from valve body.
14. Remove block vee from piston.
15. Remove four bolts which secure control valve hous­
ing to hydraulic cylinder body. Remove housing.
16. Remove control valve diaphragm spring from hous­
ing.
17. Rem ove control valve diaphragm assem bly from hy­
draulic cylinder body.
18. Separate diaphragm retainer, diaphragm , diaphragm
washer, control piston and cup seal.
19. Remove snap ring from control valve housing. R e­
move retainer and seal ring from housing.
20. Remove valve cap (press fit) and rem ove valve seat,
valve body and spring from control valve housing.
ASSEMBLY
1. Place control valve spring on valve body and insert in
housing. Install valve seat from other side and secure
with valve cap (press fit).
2. Install seal ring and retainer in housing. Secure with
snap ring.
3. Assem ble diaphragm retainer, diaphragm , diaphragm
washer, control piston and cup seal.
4. Install control valve diaphragm assem bly in hydraulic
cylinder body.
5. Place control valve diaphragm return spring in posi­
tion in housing.
6. Install housing and spring on hydraulic cylinder body
and fasten with four bolts. Tighten bolts alternately.
7. Install block vee on piston.
8. Install valve insert in valve body.
9. Assem ble valve body, piston and push rod and install
snap ring.
10. Install spacer and O-ring on push rod.
11. Install block vee on bushing.
12. Install bushing and washer on push rod.
13. Install push rod, piston and bushing assem bly in hy­
draulic cylinder body. Secure with snap ring.
14. Position gasket, front housing and reinforcem ent
plate on hydraulic cylinder body. Fasten with two
bolts.
15. Install diaphragm return spring, spacer and di­
aphragm and plate assem bly on push rod. Install lock
nut on end of push rod.
16. Install tube and nut assem bly in control valve.
17. Place rear housing in position and secure with clam p
band.
18. Install m ounting bracket on front end of hydraulic
cylinder body.
AIR BRAKES
OVERHAUL
INSPECTION AND REPAIR
SLACK ADJUSTERS
Disassembly (Fig. 1)
1. Rem ove dirt and grease from outside of unit by w ash­
ing in a suitable cleaning fluid.
2. C u t off riveted ends of rivets attaching cover plates to
body. Drive out rivets and rem ove cover plates.
3. Remove welch plug from end of w orm shaft bore. In­
sert a flat end punch into the w orm shaft bore and
drive w orm shaft out of body and worm .
4. R em ove lock sleeve and spring from w orm shaft. R e­
move gear and w orm from slack adjuster body.
1. W ash parts in cleaning fluid and wipe dry.
2. Inspect w orm and gear and replace with new parts if
chipped or broken teeth are evident.
3. Inspect w orm shaft for wear. M ake sure corners on
hex end are not rounded.
4. Inspect bushing in lever arm . If worn, out-of-round,
or otherwise dam aged, it m ust be replaced. To replace
bushing, press old bushing out and press new bushing
into place. Bushing m ust be ream ed, after installation,
to an I.D. of .501 inches plus or minus .003 inches.
5. Exam ine lock sleeve for cracks or other dam age. R e­
place if necessary.
CHEVROLET SERIES 70-80 HEAVY DUTY TRUCK SHO P M A N UA L