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2. Remove shoe return spring and discard. Force shoes
towards the S-cam to relieve spring tension. (Figure 4)
3. Remove shoes. Lift one of the shoes off anchor pin and
lower both shoes to the floor. (See Figure 5)
4. Remove the two shoe retainer springs and discard. NOTE:
If only replacing the brake shoes, no further disassembly
is required. Reverse Steps 1 thru 4. NOTE: Always install
new springs.
5. Remove the anchor pin by sliding it out of the spider.
6. Remove the cotter pin from the yoke of the actuator.
Remove yoke pin so the slack arm is free of the yoke.
Remove the two nuts and washers that secure the
actuator to the bracket and remove the actuator.
7. Remove snap ring and washer from splined end of cam
shaft. Remove slack adjuster from cam shaft. (A puller
may be required.) Remove spacers and the thick washer
from cam shaft. (See Figure 6)
8. Remove cam shaft from actuator bracket and cam tube.
9. Mark and remove the dust shields from the spider by
removing the six cap screws using a 3/8" socket. Do not
remove unless there is apparent damage (See Figure 7).
10. Remove the actuator bracket and cam tube from the
spider by removing the four cap screws and lockwashers
using a 3/4" socket.
11. Remove and discard the two cam shaft grease seals.
One at each end of the cam tube.
12. Remove and discard the two cam shaft bushings located
in the same area as the seals in Step 11. Use a tool of
proper diameter and length to drive the bushings out
from the backside. NOTE: Prior to removal see the
"Inspection of Parts" section, Step 1B.
13. To facilitate assembly, note or mark the relationship of
the spider to the axle (driver or curb side) and the
orientation on the axle flange. Remove the spider from
the axle flange by removing the five bolts, nuts, and
lockwashers and the nuts and lockwashers from the three
studs. NOTE: If the spider is to be reused and there is
damage to any of the three studs, they may be pressed
out of the spider and replaced with grade 8,
5/8" bolts.
CLEANING OF PARTS
After disassembling the foundation brake, wash the metallic
components in mineral spirits and wipe dry. Be careful not
to get any foreign material, especially grease on the brake
shoes or interior of the brake drum. Use a wire brush to
remove heavy contamination from the spider and outside of
the brake drum.
INSPECTION OF PARTS
1. ACTUATOR BRACKET AND CAM TUBE
A. Check assembly for bent actuator bracket and broken
or cracked cam tube welds.
B. Inspect cam shaft bushing for signs of wear. Bearing
surfaces should be smooth and free of any pitting or
fractures. Insert cam shaft and measure looseness
at both ends with a dial indicator. If more than .020"
movement is noted, replace bushings and/or cam
shaft. NOTE: If it is determined that a bushing
requires replacement, both cam shaft bushings
should be replaced.
2. CAM SHAFT
A. Inspect cam shaft spline for cracks and excessive
deformation. Replace as necessary.
B. Inspect the cam shaft bearing journals for wear or
corrosion. If the shaft shows wear or roughness that
is visible or roughness that can be detected by feel,
it must be replaced.
C. Inspect cam head for cracks, and its roller surfaces
for flat spots, brinneling, or ridges. Note unusual wear
patterns which may indicate an out-of-square
condition. Replace if any of these conditions exist.
3. SPIDER
A. Inspect for cracked or broken surfaces on the spider
at the cam, anchor pin, and mounting bolt holes.
Replace any spider with visible damage. Do not
attempt to weld or repair. Check fit of anchor pin in
torque spider. Radial clearance in excess of .010"
indicates excessive wear. Replace anchor pin and/
or torque spider.
4. ROLLERS AND PINS
A. Inspect rollers and pins for flat spots, galling, broken
or cracked surfaces. Replace as necessary.
5. ANCHOR PIN
A. Inspect anchor pin for worn, broken or cracked
surfaces. Replace as necessary.
6. SHOES AND LINING
A. Check shoes for bent shoe webs, cracks in shoe
table welds or webs, and elongated rivet holes.
Replace shoes if any of these conditions exist.
B. Measure the shoe span by loosely installing the
anchor pin and cam roller in the appropriate ends of
the shoe web. If the distance from center of anchor
pin to center of cam roller exceeds 11.78" replace
shoe.
C. Check linings. Replace when any of the following
conditions exist:
1. Lining thickness at thinnest point is 1/4" or less.
2. Linings are cracked or worn in an unusual or odd
pattern, i.e., lining wear tapered from side to side
across shoe table. Unusual wear patterns can
indicate damage to foundation brake parts.
3. Rivet holes are elongated in lining or shoes.
4. Lining is oil soaked.
5. Linings can be moved by hand, i.e.; loose rivets.
5
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Troubleshooting
