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TM 10-3930-638-24&P
2-43. SERVICE BRAKE MAINTENANCE (cont)
c. Hydraulic Brake Valve (cont).
(2) Power Assist Unit (cont).
STEP
LOCATION
ITEM
ACTION
REMARKS
REMOVAL
1
Front chassis,
a. Rubber cover (1)
Grasp and pull
From gland (2)
bottom left side
b. Four cap screws (3)
Loosen and remove Support body (5)
and lock washers (4)
c. Power assist unit
Remove
Pull straight from bracket until clear of
body (5)
push rod (7); then lower and remove from
vehicle
d. Rubber cover (1)
Remove and
From push rod (7)
discard
DISASSEMBLY
2
Power assist unit
a. Body (5)
Position and clamp In vise, with gland (2) facing upward
WARNING
Exercise care when removing gland (2). There will be spring ten-
sion against the gland. Failure to do so may cause gland to fly
into your eyes.
b. Gland (2)
Loosen and remove Turn counterclockwise using spanner
wrench or chain wrench and pull from
body (5)
c. Spool (9), piston
Remove
Pull from body (5)
(10) and spool cap
(11)
d. Piston (10)
Remove
From spool (9)
e. Piston ring (12)
Remove and
Use piston ring pliers
discard
f. Spring retainer(13)
Remove
Pull from body (5)
and spring (14)
g. Body (5)
Reposition and
In vise, with gland end facing down
clamp
h. End plug(15)
Remove
From body (5)
i. O-ring ( 16)
Remove and
discard
j. Spring (17), shim(s)
Remove
From body (5)
(18) and poppet (19)
NOTE
Spring (17) and shim(s) (18) are matched set. Retain shim(s) for
reassembly with original spring (17).
3
Gland (2)
a. O-ring (20)
Remove and
From gland (2)
discard
b. O-ring (21), U-cup
Remove and
From bore in gland (2)
seal (22) and backup
discard
ring (23)
2-304
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