GMC 1976 ZEO 6083 Maintenance Manual page 471

e. Restricted oil feed to forward clutch (Ex-
amples : Clutch housing to inner and outer areas not
drilled, restricted or porosity in pump) .
f. Pump cover oil seal rings missing, broken
or undersize; ring groove oversize .
g. Case valve body face not flat or porosity
between channels .
h. Manual valve bent and center land not
ground properly .
2. Intermediate Clutch .
a. Rear accumulator piston oil ring, damaged
or missing.
b. 1-2 accumulator valve stuck in control
valve assembly.
c . Intermediate clutch piston seals damaged
or missing.
maged.
d. Center support bolt loose.
e. Low line pressure.
f. Case valve body face not flat or porosity
between channels .
g. Manual valve bent and center land not
ground properly .
3. Direct Clutch .
a. Restricted orifice in vacuum line to
modulator (poor vacuum response .)
b. Check ball in direct clutch piston damaged,
stuck or missing.
c. Defective Modulator bellows.
d. Center support bolt loose. (Bolt may be
tight in support but not holding support tight to
case) .
e. Center support oil rings or grooves da-
maged or missing.
f. Clutch piston seals damaged or missing.
g. Front and rear servo pistons and seals da-
h. Manual valve bent and center land not
cleaned up .
i. Case valve body face not flat or porosity
between channels .
wards.
TRANSMISSION 7- 2 3
j. Intermediate sprag clutch installed back-
k. 3-2 valve, 3-2 spring or 3-2 spacer pin in-
stalled in wrong location in 3-2 valve bore .
1. Incorrect combination of front servo and
accumulator parts.
m. Replace intermediate clutch piston seals.
NOTE :
If direct clutch plates and front band are
burned, check manual linkage.
VACUUM MODULATOR ASSEMBLY
The following procedure is recommended for
checking Turbo Hydra-matic modulator assemblies
in the field before replacement is accomplished .
1 . Vacuum Diaphragm Leak Check. Insert a pipe
cleaner into the vacuum connector pipe as far as
possible and check for the presence of transmission
oil. If oil is found, replace the modulator.
CAUTION : Gasoline or water vapor may set-
tle in the vacuum side of the modulator. If
this is found without the presence ofoil, the
modulator should not be changed.
2. Atmospheric Leak Check. Apply a liberal
coating of soap bubble solution to the vacuum con-
nector pipe seam, the crimped upper to lower hous
ing seam, and the threaded screw seal . See Figure 11 .
Using a short piece of rubber hose, apply air pressure
to the vacuum pipe by blowing into the tube and
looking for bubbles. If bubbles appear, replace the
modulator.
LOWER HOUSING
VACUUM CONNECTOR
SEAM
HOUSING SEAL
SLEEVE
PLUNGER
R_J]N
Figure 1 1-Modulator Assembly