TRUCK SERVICE MANUAL
SERVICING POWER UNITS
AIR CHAMBER DIAPHRAGM
A. Manual Adjusters.
Jack or hoist wheels free of ground.
The following procedures are used to replace the
Remove dust cover from adjusting slot two
diaphragm and boot with the non-pressure housing on /
places on each brake.
the brake assembly.
On RD type brakes the adjusting slots are below
A. Refer to PARKING BRAKE SECTION for removal of
the forward and above the rear power unit.
spring brake air chambers.
If star-wheel adjusting bolts are not found at
these positions, the brake had been assembled
B. Remove air lines and tag emergency line.
on the wrong side of the vehicle.
C. Remove clamp ring nuts, bolt
Adjusting bolts have right hand threads. With an
adjusting spoon, turn the star-wheel until a
heavy drum drag is developed. Then back off
the bolt to a very light drag on the drum.
Repeat for other shoe on the brake. Replace
dust covers in adjusting slots. Repeat for other
NOTE: Recommended adjusting spoons, are Snap-On-
Blue-Point S-9523, Wizard 4-H-2530 and Proto 2006.
D. Spread the clamp ring. Hold the diaphragm on the
non-pressure half and remove the pressure half
Carefully remove the diaphragm while holding
diaphragm plate against the wedge rod. This will prevent
the wedge assembly from coming out of engagement
with the plungers.
B. Automatic Adjusters
Check drum to lining clearance with feeler gage.
NOTE: If wedge assembly backs out of plunger anytime
If the clearance is more than .060", adjust
during this entire procedure, remove non-pressure
brake manually (same as above) and schedule