Chevrolet 10 Series 1968, Service Manual

Page: 210 / 713

REAR SUSPENSION AND DRIVE LINE 4-41
cylinder assembly from the differential carrier
housing.
3. Remove the two retaining bolts and lock washers at­
taching the vacuum cylinder to its housing and sepa­
rate the two assemblies.
4. Remove the screws that attach the two halves of the
vacuum cylinder and remove the outer half.
5. Remove the diaphragm plates, and shaft as an
assembly.
6. Drive the old seal out of the housing.
7. Soak new seal in engine oil to provide for initial lu­
brication. Coat outer diameter of seal with Perma-
tex and replace it in the inner half of the cylinder
with the free side of the seal lip down and press it
into place with seal installer Tool J-*(!!f968.
8. Assemble the diaphragm shaft assembly into the
housing.
9. Install the outer cover, and retaining screws.
CA U TIO N : Install the cover with the vacuum
line connection aligned with the connection on the
lower outer cover.
10.' Assemble the vacuum cylinder assembly into its
housing, install the two retaining bolts and lock
washers and tighten securely.
NOTE:
The felt seal and felt seal in the hous­
ing should be inspected for damage and replaced
when necessary.
11. Install the completed assembly to the carrier housing
with new gasket and the three retaining bolts and lock
washers and tighten securely.
12. Replace the hose connections and install clamps.
13. Test the operation of the shifting mechanism in all
speeds.
SHIFTER SPRING
Replacement
1. Follow instructions given in Steps 1, 2, 3, 4 under
“ Vacuum Cylinder Diaphragm Replacement.”
2. Remove the piston rod from the housing.
3. Push in on end of piston rod to relieve spring load
and remove snap ring from inside of piston rod. Pull
push rod assembly out of piston rod.
4. Place head of push rod bolt in bench vise and remove
two nuts, short spacer, stop washer, spring, long
spacer, and stop washer from push rod bolt.
5. Install stop washer, long spacer, new spring, stop
washer and short spacer.
6. Install adjusting nut on push rod and tighten until
distance between outer faces of stop washers is
2-13/16" (fig. 84).
7. InstalL-iocknut on push rod and tighten, being careful
not to change the 2-13/16" adjustment.
8. Lubricate inside of piston rod with engine oil and
install push rod assembly.
9. Push in on push rod to compress spring and install
snap ring.
10. Install push rod assembly in the housing.
11. Complete the assembly of the vacuum cylinder ac­
cording to instructions given in Steps 5, 6, 7, 8, 9
under “ Vacuum Cylinder Diaphragm Replacement.”
VACUUM SHIFT UNIT CONTROL SWITCH
Replacement
The manually operated control switch, mounted on the
transmission shift lever (fig. 85) is an electromechanical,
two-position switch which controls the axle vacuum shift
unit and the associated speedometer adapter.
1. Disconnect switch electrical leads at the dash panel
mounted fuse block and speedometer adapter.
2. Remove the two screws securing the axle shift con­
trol valve to the frame side member mounted
bracket.
NOTE:
Do not disconnect control valve vac­
uum, atmosphere or air cleaner lines.
3. Tilt or slide control valve as required to obtain ac­
cess to cable retaining screw and disconnect cable
from valve (fig. 86). Disconnect conduit from valve
assembly and remove all cable retaining clips.
4. Remove the transmission shift lever knob, then re­
move the two screws retaining switch housing to
transmission shift lever and withdraw cable and
housing assembly from vehicle.
5. Make sure cable shift knob is in down position, then
attach switch housing rubber case on transmission
shift lever so that the distance from top of cable
shift knob to top of transmission shift lever is
Fig. 84 —A djusting Push Rod
Fig . 85 —Shift Unit Control Switch
CHEVROLET TRUCK SERVICE MANUAL