GMC 1976 ZEO 6083 Maintenance Manual page 207

OVERTRAVEL LEVER CENTER POSITION
ADJUSTMENT
1 . Clean exterior of control valve assembly .
2 . Remove cover and rubber O-ring from valve
assembly, then drain off the Silicone fluid.
3 . Remove exhaust fitting (15, figure 49) and
exhaust screen (13, figure -49) from control valve.
4. Referring to Figure 51, scribe a line 1-3/8 inch
from plug end of overtravel lever control body .
5. Place control valve assembly in vise as shown
in Figure 53 .
6. If vacuum source is available, attach supply
hose to valve exhaust port (figure 50) using Sun
Tester fitting #115-3 or equivalent. Do not apply
vacuum at this time .
7. Attach air pressure supply hose to air inlet port
(figure 50). Do not apply pressure at this time .
8 . Locate dial indicator in position as shown in
Figure 51 . Move overtravel lever to full air exhaust
position - TOP OF DELAY PISTON FLUSH
WITH TOP OF BORE - without overtraveling (po-
sition "C," figure 52). Relocate indicator push rod to
just contact 1-3/8-inch mark on control body and
reset indicator dial to zero at this point (position
"C", figure 42).
9 . Move overtravel lever to full air intake position
without overtraveling (position "A", figure 52)
(delay piston at bottom of bore). Take indicator read-
ing which may vary from 0.160" to 0.190" .
10 . Repeat Steps 8 and 9 above to recheck this
reading.
Figure 50-Height Control Valve Port Identification
REAR SUSPENSION 4- 23
Figure 51-Dial Indicator Properly Installed
11 . Divide the total travel dimension by two (ex-
ample: 0.170" - 2 = 0.085"), then move overtravel
lever back this amount (0 .085") to the center (posi-
tion "B," figure 52).
IMPORTANT :
Without disturbing lever center
position, reset indicator dial to zero, which actu-
ally is 0.100" on indicator of type registering
IO
Dial Indicator
(Minimum
Range 0 .200")
Valve Assembly
Retained
Horizontally
"B" Lever
Center Position
TPM-8412
Figure 52-Locating Valve Overtravel Lever Center
Position