Brake Shoe Relining; Brake Drums; Hydraulic Brakes - GMC 4000 Series Service Manual

4. Install the other brake shoe in same man­
ner as described in paragraphs 2 and 3.
5. Install long brake shoe return springs in
shoe web, longest shank at adjuster, and hook
springs over pins.
6. Install short brake shoe return springs in
shoe web and hook springs over pins at anchor
end.
7. Place adjuster eccentrics on shoe webs and
fasten with self-tapping screw. Tighten screw only
finger-tight to permit final adjustment later.
8. Place adjuster cranks on anchor pins, their
long arms toward shoes, bushing toward backing
plate, so that they rotate freely while resting
against return spring hooks.
9. Install and crimp adjuster crankC-washer.
10. Place star wheel crank on anchor support
and fasten with crank bolt.
11. At each adjuster crank assemble the short
link sm all hook into the short arm of the crank
from the lower side and hook the other end of link
around the eccentric on the shoe web.
12. Assem ble long link "S" hook to long arm
of adjuster crank from upper side, rotate star
wheel crank so that slot lines up with link "U" hook.
Insert "U" hook and rotate star wheel crank back
to approximate adjusting position.
13. Install adjuster spring with short hook on
star wheel crank finger so that its long shank hook
assem bles on the outer groove of the pin from the
wheel cylinder side.
Brake linings on these models are riveted to
the brake shoes and may be replaced. These lin­
ings may be purchased in replacement sets of four
linings and sufficient rivets of correct specifica­
tions. Refer to Parts Book for lining replacement
kits. When replacing linings, make sure that shoes
Brake drum installations are illustrated in
"FRONT HUBS AND BEARINGS" (SEC. 3D) and
"REAR HUBS AND BEARINGS" (SEC. 4C) of this
manual. Procedures for replacing brake drums
are also included in the above mentioned sections.
Whenever brake drums are removed for serv­
icing brakes, inspect drums. If found to be scored,
rough, or out-of-round, drums should be machined.
Machining or grinding of brake drums in­
creases the inside diameter of the drum and chang­
es the lining to drum fit. When machining drums,
G M C S E R V I C E M A N U A L
INITIAL MANUAL LINING ADJUSTMENT
wheel adjustments.
backing plate curl and shoe (do not mar lining).
Slide shoe up or down in anchor slots until leading
and trailing edges of the lining are equidistant
from the inner curl of the brake backing plate.
required, until linkage aligns star wheel crankpawl
with center line of star wheel screw. A SMALL
DRILL POINT RECESS ON THE ANCHOR SUP­
PORT IS THE ALIGNING MARK.
self-tapping screw s to 19 foot-pounds torque.
HUBS AND BEARINGS" (SEC. 4C) of this manual.
back of backing plate.
wheel until lining drags on drum while drum is
rotated. To tighten adjustment, move tool handle
toward axle while using inner side of adjuster slot
as fulcrum for the tool, rotating the star wheel
teeth away from the axle.
forward, until drag is just relieved. Provide ad­
ditional running clearance by backing off 8 to 10
more notches and replace slot covers. Automatic
adjustment now takes over.

BRAKE SHOE RELINING

are clean and that linings are installed in a manner
that will prevent gaps between lining and shoe.
should be used. Make sure lining fits firmly against
shoe, and that rivets are properly upset.
BRAKE DRU M S
it is recommended that the following maximum
oversizes not be exceeded:
imum lim its does not provide a suitable braking
surface, discard the worn drum and replace with
a new standard drum.
SAFETY PRECAUTION.

HYDRAULIC BRAKES

1. If shoes have been relined, back off star
2. Center each shoe; insert a pry tool against
3. On each shoe web, rotate hex eccentric, as
4. When aligned, lock eccentrics by tightening
5. Install hub and drum as described in "REAR
6. Remove both adjustment slot covers from
7. Insert adjusting tool and turn each star
8. Back off star wheels while rotating drum
Conventional lining replacement equipment
(a) Drums with standard diameter up to 14"
can be machined up to 0.060" oversize.
(b) Drums with standard diameter over 14"
can be machined up to 0.080" oversize.
When it is found that machining to these max­
DO NOT EXCEED THESE LIMITS. THIS IS A
Sec. 5A
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