Chevrolet 10 Series 1970, Service Manual

Page: 273 / 671

BRAKES 5-35
tube seat tangent to cylin d er b o re. Upper c y l­
inder has threaded b le e d e r va lve opening d r ille d
at extrem e outer edge o f cylin d er bore. C y l­
inders must be positioned with connecting tube
openings toward each other. (Top port on bottom
cylin d er, bottom p ort on top cylin d er).
1. P osition heat shields on cylin d er, place wheel c y lin ­
d ers on flange plate, and attach with cap screw s and
lock w ashers. Tighten cap screw s fir m ly .
2. Install connecting tube between the two cylin d ers and
tighten connections fir m ly . Connect brake tube to
in let opening bottom p o rt in lo w e r cylin d er at inner
side o f flange plate. In stall b le e d e r va lve in threaded
opening in upper cylin d er top p o rt at inner side of
flange plate.
3. Install brake shoes as d irected under “ Brake Shoe
In stallation .” B leed brake system as p revio u sly
d irected under "B le e d in g Brakes.
”
Type “ F”
NOTE: The two w heel cylin d ers mounted on
each brake are iden tical; how ever, cylin d ers on
righ t-an d-left-h an d brakes have opposite c y lin ­
d er castings. Clean mating su rfaces o f cylin d ers
and flange plate to insure p ro p er alignment.
1. P la ce each cylin d er on flange plate and attach with
one la rg e and two sm a ll cap screw s and lock
w ashers.
2. P osition wheel c y lin d e r connecting tube and fittin g
assem bly and attach fittin g to lo w e r opening in upper
cylin d er with in let connector, using new copper g a s ­
ket on both sides o f fittin g. Attach fittin g to low er
opening in lo w er c y lin d e r with sp ecia l bolt, using
new copper gasket on both sides o f fittin g. Tighten
in let connector and sp ecial bolt fir m ly .
3. In stall b leed er va lv e in upper opening in each
cylin d er.
4. Install brake shoes as d irected under "B r a k e Shoe
In stallation .” B leed brake system as p reviou sly
d irected under "B le e d in g B ra k e s .”
Type “ FR-3”
NOTE: Upper and lo w e r wheel cylin d ers on
both right-and left-hand brakes are in terch an ge­
able. C ylin ders must be positioned on flange
plate so that the long stroke end o f the cylin d er
fa ces the shoe toe (adjustm ent end o f shoe) o r
the adjusting slot in backing plate. Make sure
mating surfaces o f cylin d ers, heat shields, and
flange plate are clean to assure p ro p er
alignm ent.
1. P o sitio n heat shield on each w heel cylin d er, and in ­
s ta ll on flange plate. Attach each cylin d er with two
cap screw s and lock w ashers.
2. Attach connecting tube fittin g to lo w e r opening in the
upper cylin d er, and to the upper opening in the low er
cylin d er. In stall b le e d e r s c re w in upper opening o f
the upper cylin d er. Connect brake line at lo w er
cylin d er fitting.
3. In stall brake shoes as d irected under "B r a k e Shoe
In sta lla tion .” B leed brake system as p revio u sly
d ire c te d under “ B leedin g B ra k e s . n
BRAKE DRUMS
A ll fron t brake drums except those used on 3/4 and 1
ton trucks a re the non-demountable type, that is , they
cannot be rem oved without rem ovin g the hub. W henever
this type drum is rem oved, wheel bearings must be ad­
justed as outlined in Section 3. R ea r brake drums on
som e m odels are demountable, that is, they may be r e ­
m oved without rem ovin g the wheel hub. (See Section 4,
Hub and Drum R em oval).
Rem oval
Front
1. Jack up fron t end o f v e h icle and rem ove wheel.
2. R em ove hub and brake drum assem bly.
NOTE: 3/4 and 1 ton drums may be rem oved by
rem oving 2 slotted head screw s which retain
drums to hub. On a ll other m odels, hub and
drum a re rem oved as an assem bly.
3. Rem ove brake drum fro m hub as outlined in S ec­
tion 3.
Rear
1. Jack up re a r end o f veh icle and rem ove wheel.
2. R em ove countersunk screw s, where used, and r e ­
m ove brake drum fro m outer flange o f hub.
Inspection and Reconditioning
W henever brake drums a re rem oved they should be
thoroughly cleaned and inspected fo r crack s, s c o re s , deep
g ro o v e s and out-of-round. Any o f these conditions must
be co rrected .
Smooth up any sligh t s c o re s by polishing with fine
e m e ry cloth.
An out-of-round drum m akes accurate brake shoe
adjustment im p ossib le and is lik ely to cause ex c e s s iv e
w ear o f other p arts o f brake m echanism due to its
e c c en tric action.
O ut-of-round, as w e ll as taper and w ea r can be a c ­
cu rately m easured with an inside m ic ro m e te r fitted with
p ro p er extension rods.
Machining o r grinding o f brake drums in crea ses the
inside diam eter o f the drum and changes the lining to
drum fit. When machining drums, it is recom m ended
that the follow in g m axim um o v e r s iz e s not be exceeded:
(a) Drums with standard d iam eter up to 14" can be
machined up to .060" o v e r s iz e on the d ia m e te r.
(b) Drums with standard d iam eter o v e r 14" can be
machined up to .080" o v e r s iz e on the d ia m e te r.
When it is found that machining to these maximum
lim its does not p rovid e a suitable braking su rface, d is ­
card the worn drum and replace with a new standard
drum.
CA UTIO N: Drums must not be turned m ore
than .080" la r g e r than the o rig in a l d ia m eter.
Installation
1. Make sure mating su rfaces o f hub, drum and o il
d e fle c to r a re clean and smooth and assem ble as out­
lined in Section 3.
2. On front, in sta ll drum and hub assem bly to wheel
spindle and adjust bearin gs on 1/2, 11/2 and 2 ton
as outlined in Section 3. On 3/4 and 1 ton in stall
drum and retain in p lace with retaining screw s.
3. On re a r, assem ble drum assem bly o v e r hub studs
and in stall retaining screw s, if used.
CHEVROLET TRUCK SERVICE MANUAL