GMC 4000 Series Service Manual page 262

anchor bracket is placed over anchor bar.
2. Install anchor screw through bracket and
spring into anchor bar. Insert locating bolt up
through band lower bracket and hole in support
and install nuts temporarily.
3. Place operating cam s between links and
install new clevis pin and cotter pin.
4. Insert threaded end of adjusting bolt down
between operating cams with hook toward rear of
vehicle. As bolt is lowered into place it must pass
through cam shoe, band upper bracket, upper re­
lease spring, brake support, lower release spring,
and band lower bracket. Install tension spring, flat
washer, adjusting nut, lock washer (if used), and
lock nut on adjusting bolt.
5. Adjust lining to drum clearance and con­
nect brake rod as directed under "Band Type Ad­
justment."
BRAKE DRUM REMOVAL
1. Remove brake band and lining assembly.
2. Remove nuts and lock washers from bolts
attaching propeller shaft U-joint flange and brake
drum to transm ission output shaft flange. T eles­
cope propeller shaft at slip joint and lower end of
propeller shaft to floor. Remove if necessary, nuts,
The two-shoe duo-grip type brake consists of
two brake shoes operating on a brake drum attach­
ed to transmission mainshaft flange in conjunction
with the propelller shaft (fig.
Linkage connecting parking brake lever to
operating lever at brake varies on different models,
however, adjustment is made at brake assembly
on all models in same manner.
BRAKE ADJUSTMENT (Fig. 2)
1. Place parking brake lever in fully released
position.
2. Loosen lock nut (12) and adjust bolt (13) as
necessary to obtain 0.010" to 0.015" clearance be­
tween outer shoe lining and brake drum at a point
directly above adjusting bolt (13). Hold bolt and
tighten lock nut securely.
3. Loosen lock nut (
necessary to obtain 0.010" to 0.015" clearance be­
tween inner shoe lining and drum. Hold nut (11) and
tighten lock nut ( ).
6
4. Recheck lining to drum clearance. Final
clearance between both linings and drum must be
0.010" to 0.015".
BRAKE SHOE REMOVAL (Fig. 2)
1. Remove adjusting nut (11) and disengage
link from operating lever.
2. Loosen adjusting bolt lock nut (12) and back
G M C S E R V I C E M A N U A L
TWO-SHOE (DUO-GRIP) PARKING BRAKE
).
2
) and adjust nut (11) as
6
lock washers, and bolts attaching propeller shaft
center bearing hanger bracket to crossmember.
3. On some vehicles, brake drum is mounted
on forward side of transm ission mainshaft com­
panion flange, and on other vehicles it is mounted
on rear side of flange. If mounted on rear side of
flange, drum may be removed without removing
flange; if mounted on forward side of flange, re­
move retaining nut and flange from output shaft.
Press serrated bolts from flange to remove drum.
BRAKE DRUM INSTALLATION
1. Wipe mating surfaces of brake drum and
output shaft flange clean. Position brake drum on
flange and press serrated bolts into place. Replace
drum assembly and retaining nut on output shaft.
Refer to "TRANSMISSION ON-VEHICLE SERVICE
OPERATIONS" for nut torque on various transm is­
sion models.
2. Position propeller shaft flange against brake
drum (or output shaft flange). If removed, attach
propeller shaft center bearing hanger bracket to
crossm em ber. Replace all lock washers and nuts
and tighten securely.
3. Install brake band and lining assembly and
adjust brake.
off adjusting bolt (13) until it clears the brake shoe
web. Unhook return spring from outer shoe.
3. Remove lock from outer shoe upper pivot
pin and slide shoe and operating lever assembly
off pivot pin and brake drum.
4. Place shoe and operating lever assembly
on bench. Remove lock rings securing brake shoes
on operating lever pins and remove shoes from
pins.
LINING REPLACEMENT
1. Remove linings from shoes, using deliner
punch in a brake relining machine.
. Clean all dirt and corrosion from shoes,
2
using a wire brush if necessary.
3. Install new linings on shoes, installing
rivets in center holes first. A 0.010" feeler must
not enter between lining and shoe at any point.
BRAKE SHOE INSTALLATION (Fig. 2)
1. Install brake shoes on operating lever pins
and secure with lock rings.
2. Install shoe and operating lever assembly
on brake drum, with upper end of outer lever in
place on pivot pin. Install lock on pivot pin.
3. Insert link through operating lever, with
washer and spring in place on top of lever. Install
adjusting nut (11) on link. Connect return spring to
outer shoe.
Sec. 5C
Page 254A
PARKING BRAKES