Chevrolet 10 Series 1970 Service Manual page 258

BRAKES 5-20
bly. This action adjusts the shoes until clearance between
the lining and drum is within p ro p er lim its.
Should low pedal heights be encountered, it is r e c ­
ommended that numerous forw a rd and re v e rs e stops be
p erfo rm e d with a fir m pedal e ffo rt until a sa tisfa cto ry
brake pedal height resu lts.
NOTE: Frequent usage of an automatic tra n s­
m ission fo rw a rd range to halt re v e rs e ve h icle
motion may preven t
fro m functioning, thereby
heights.
Retracting Self Adjusters (Fig. 3 5 )
A lanced "k n ock out" a rea is p rovided in the web o f
the brake drum on a ll m odels except the P20, P30 and 50
and the re a r w heels of the K20 and C30. On these m odels
the access hole is located in the flange plate. This hole is
fo r s e rv ic e purposes in the event retractin g o f the brake
shoes is requ ired to rem ove the drum. H ow ever, in o rd er
to back o ff the adjuster, it w ill be n ecessa ry to hold the
actuating le v e r away fro m the starwheel.
Brake Drums, Shoes and Linings
NOTE: If brake drums a re worn s e v e re ly , it
may be n ecessa ry to re tra c t the adjusting screw
as p revio u sly outlined.
C A U TIO N : A fte r knocking
sure to rem ove it fro m the inside o f the drum
and clean a ll m etal fro m the brake com partm ent.
A new hole c o v e r must be installed when drum
is re in sta lled .
Removal (Figs. 36 and 3 7 )
1. R aise the veh icle on hoist o r place on jack stands.
2. Loosen check nuts at forw ard end o f parking brake
cable su fficien tly to rem ove a ll tension fro m brake
cable.
3. Rem ove brake drum s.
NOTE: Since boots a re rec es se d in g rooves on
wheel cylin d ers to p reven t pistons fro m leaving
cylin d ers, it is not n ecessary to in stall wheel
cylin d er clam ps when brake shoes a re rem oved;
how ever, brake pedal must not be dep ressed
while drums are rem oved.
4. Unhook brake shoe pull back springs fro m anchor pin
and link end, using T o o l J-8049.
5. R em ove the actuator return spring.
6. Disengage the link end fro m the anchor pin and then
fro m the secondary shoe.
7. Rem ove hold-down pins and springs using any suit­
able tool.
8. R em ove the actuator assem bly.
NOTE: The actuator, p ivot and o v e rrid e spring
a re an assem bly. It is not recom m ended that
they be disassem bled fo r s e r v ic e purposes, un­
le s s they a re broken.
assem ble and d isassem b le the brakes by leaving
them intact.
9. Separate the brake
sc re w and spring.
the automatic adjusters
inducing low pedal
out the m etal, be
It is much e a s ie r to
shoes by rem oving adjusting
SECONDARY SHOE
OVERRIDE
SPRING
ACTUATING LEVER
STAR WHEEL
F ig . 3 4 —S e lf A d ju s tin g Brakes
10. Rem ove parking brake le v e r fro m secondary brake
shoe (r e a r only).
11. Clean d irt out o f brake drum using care to avoid
getting d irt into front wheel bearin gs. Inspect drums
fo r roughness, scorin g o r out o f round. Replace o r
recondition drums as n ecessary.
12. Inspect wheel bearings and o il seal and replace any
n ecessa ry parts.
13. C a refu lly pull lo w er edges of wheel cylin der boots
away fro m cylin d ers and note whether in te rio r is wet
with brake fluid. E xcessive fluid at this point in di­
cates leakage past piston cups requ irin g overhaul o f
wheel cylinder.
NOTE: A slight amount o f fluid is n early a l­
ways present and acts
piston.
14. If working at re a r wheels, inspect backing plate fo r
o il leakage past axle shaft o il seals. In stall new seals
if n ecessary.
15. Check a ll brake flange plate attaching bolts to make
F ig . 3 5 —Brake A d ju s te r Access H ole
ANCHO R PIN
PULL BACK
SPRINGS
HOLD DOW N
SPRING A N D PIN
as lubricant fo r the
CHEVROLET TRUCK SERVICE MANUAL