Chevrolet 70 1969 Series, Shop Manual

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T R A N SM ISSIO N S A N D CLUTCHES 7D-26
IM P O R T A N T : It is better to have push rod ad­
justed too short than for it to be too long.
A L L M O D E L S
While pressing clutch pedal with hand, check
for clearance between the push rod and piston. If
necessary, loosen lock nut on master cylinder push
rod assembly, then turn hex portion of push rod
(fig. 9) as necessary to provide 0 to 1/8-inch free-
travel measured at pedal pad before push rod con­
tacts master cylinder piston. After making adjust­
ment, tighten lock nut on push rod.
IM P O R T A N T : Make sure piston contacts snap
ring in cylinder bore when pedal is released. In­
stall boot to master cylinder.
SLAVE CYLINDER PUSH ROD
CHECK AND ADJUSTMENT
This procedure is generally required period­
ically to compensate for clutch facing wear. Pur­
pose of adjustment is to maintain a definite clear­
ance between the release bearing and the clutch
release fingers with clutch engaged. See figure 4.
N O T E : A tool for checking clearance or the
push rod nut position can be improvised locally.
See figure 9 which shows dimensions of tool. A
short ruler can be used to measure clearance if
tool cannot be made available. Adjustment is nec­
essary when this clearance at the wedge is reduced
to or near 1 / 4-inch. The proper clearance between
wedge and adjusting nut should measure 1/2-inch.
Figure 9— Push Rod Clearance Checking Tool
Figure 10— Checking Push Rod Clearance
Using Small End of Tool
The following describes adjustment procedure
using special tool:
1. Disconnect the slave cylinder return spring.
2. With the push rod and piston seated in the
slave cylinder, push clutch fork and wedge on push
rod away from the slave cylinder. Insert smaller
end of gauge on push rod between the adjusting nut
and wedge (fig. 10). If the tool will not go between
the nut and wedge the push rod needs to be adjusted.
If the small tool end fits between the adjusting nut
and wedge, the rod does not require adjustment.
3. To adjust the push rod, use the thicker end
of the tool and insert between adjusting nut and
wedge on the slave cylinder push rod (fig. 11).
Back off adjusting nut until the tool just fits be­
tween the nut and wedge.
4. Remove the tool, lock adjusting nut with
lock nut and install the slave cylinder return spring.
BLEEDING HYDRAULIC SYSTEM
Use only Hydraulic Brake Fluid recommended
in L U B R IC A T ION (SEC. 0). When other than rec­
ommended fluid has been used, drain and flush the
entire hydraulic system, using clean alcohol or a
hydraulic brake system cleaning fluid. Refill sys­
tem with R E C O M M E N D E D fluid.
The need for bleeding air from system is gen­
erally indicated by a springy, spongy pedal action.
The presence of air in system is a result of low
fluid level in master cylinder, or if some part of
system has been opened. Bleeder valve is provided
at the slave cylinder (fig. 12).
CHEVROLET SERIES 70-80 HEANfY DUTY TRUCK SH O P M A N U A L