Chevrolet 10 Series 1970 Service Manual page 244

BRAKES 5-6
Removal
1. Disconnect battery cables.
2. Disconnect e le c tr ic a l lead fro m switch (under dash).
3. Rem ove screw s holding switch and rem ove switch.
NOTE: This switch is
s e rvic e a b le item . I f
replaced.
Installation
1„ In stall switch in r e v e r s e o rd e r of rem o v a l and follow
adjustment procedu re below.
Adjustment
1. With the brake pedal pulled back against the stop
lamp switch bracket bumper " A " and brake failu re
warning switch le v e r " B "
brake pedal bracket, snug up screw s.
2. R em ove the push rod fro m the brake pedal.
3. Apply the brake pedal fa r enough to in stall tool
J-23449-2 on School Bus (painted y ello w ) o r J-23449
on other m odels (painted blue) between the pedal
arm and the rubber bum per see F igu re 10. A llo w the
NOTE: A ll brake attachments are im portant
attaching parts in that they could affect the
p erform an ce of v ita l components and system s,
and/or could resu lt in m ajor rep a ir expense.
They must be rep laced with parts of the sam e
part numbers o r with equivalent parts if r e ­
placem ent becom es n ecessary.
placem ent parts of le s s e r quality or substitute
design. Torque values must be used as sp ecified
during reassem b ly to assure p rop er retention of
these parts.
In any s e rv ic e operation it is e x trem ely im portant that
(
RUBBER
X BUMPER
BRAKE
PEDAL
Fig . 10—Pedal T ra v e l Tool In sta lle d
a non-adjustable, non-
d efective, it must be
" C"
rid in g pin on the
MAINTENANCE AND ADJUSTMENTS
Do not use r e ­
brake pedal and tool to r e s t against the rubber
bumper.
4. Connect a test light across the switch. (Ignition un­
fused to sw itch.)
5. If the lamp is off, rotate the bracket upward until the
test light " j u s t " com es on.
6. If the lamp is on, rotate the bracket downward until
the test light " ju s t " goes out.
7. Hold the bracket in this position and tighten the
screw s to 18 ft. lbs.
8. R em ove the test light.
9. Connect the e le c tr ic a l lead to the switch and test the
operation at the dash o r windshield header warning
light.
NOTE: The brake fa ilu re warning ligh t should
com e on at approxim ately 60° of available brake
pedal tra v el.
10. Connect the push rod to the brake pedal. Install the
attaching bolt and nut. Torque nut to 30 ft. lbs. In­
sta ll the cotter pin.
absolute clean lin ess be observed. Any fo reig n m atter in
the system w ill tend to clog the lines, ruin the rubber
cups of the wheel and main cylin d ers and cause in efficien t
operation o r even fa ilu re of the braking system . D irt o r
g rea se on a brake lining w ill cause that brake to grab
fir s t on brake application and fade out on heavy brake
application.
BRAKE SHOE ADJUSTMENT
The du o-servo and Tw inplex brakes used on all 10 thru
50 s e rie s m odels are equipped with self-a d ju stin g m ech­
anism s to compensate fo r norm al facin g w ear.
s e r ie s m odels are equipped with W agner manually o r
s e lf adjusted brakes; the adjustment is made through an
opening in the flange plate o r extern a lly as outlined
below.
W ag n er Type " F" (M a n u a l Adjustm ent)
1. Jack up axle. P la c e wrench on one adjusting cam
stud to adjust one shoe (fig. 11). Rotate wrench in
d irection of fo rw a rd wheel rotation to d ecrea se lin ­
ing to drum clearan ce. Reduce clearan ce until brake
drag is fe lt as wheel is turned in fo rw a rd d irection
by hand. (Do not fo rc e adjusting cam .)
2. M ove wrench sligh tly
brake drag is relie ved , then m ove wrench an addi­
tional 7 to 10 d eg rees to p rovide running clearance
(7 to 10 d eg ree s is equal to 1 to 1 1/2 inches of tra v e l
at end of an 8-inch wrench).
3. P la c e wrench on opposite adjusting cam stud and
adjust second shoe
W a g n er Type " FR-3" (M a n u a l A djustm ent)
1. Jack up wheels until c le a r of flo o r. Rem ove adjusting
hole co ve rs fro m backing p la te.
2. A t one adjusting slot, in sert suitable tool such as
J-4707 through slot and engage adjusting w heel (fig .
Sixty
in opposite direction until
by repeating Steps 1 and 2.
CHEVROLET TRUCK SERVICE MANUAL