GMC 1976 ZEO 6083 Maintenance Manual page 469

CAUSES OF LOW LINE PRESSURE
1 . Low Transmission Oil Level.
maged.
tioned .
2. Modulator Assembly
3 . Filter .
a. Blocked or restricted .
b. "O" Ring on intake pipe omitted or da-
c. Split or leaking intake pipe .
d. Wrong filter assembly .
4. Pump .
a. Pressure regulator or boost valve stuck.
b. Gear clearance, damaged worn . (Pump
will become damaged if drive gear is installed back-
wards, or if converter pilot does not enter crankshaft
freely) .
c. Pressure regulator spring, too weak .
d. Not enough spacers in pressure regulator .
e. Pump cover plate to case gasket misposi-
f. Pump body and/or pump cover plate. Ma-
chining error or scoring of pump gear pocket .
g. Mismatch pump cover/pump body .
5. Internal Circuit Leaks.
a. Forward clutch leak (pressure normal in
neutral and reverse-pressure low in drive) .
1 . Check rings on driven sprocket support
housing for damages.
b. Direct clutch leak (pressure normal in neu-
tral, low, intermediate, and drive-pressure low in
reverse) .
age.
2. Check forward clutch seals for damage .
3. Check turbine shaft journals for distress .
4. Check stator shaft bushings for damage .
1 . Check center support oil seal rings.
2. Check direct clutch outer seal for dam-
6. Case Assembly .
1 . Vacuum Leak .
c. Improper engine vacuum .
2. Damaged Modulator.
a. Stuck valve.
b. Water in modulator.
c. Not operating properly .
3. Detent System .
b. Detent wiring shorted.
TRANSMISSION 7- 2 1
3 . Check rear servo and front accumula-
tor pistons and rings for damage or missing.
a. Porosity in intake bore area .
b. Lo-reverse check ball mispositioned or
missing (this will cause no reverse and no overrun
braking in Lo range) .
*There is no approved service procedure for
checking or cleaning the filter . If the filter is sus-
pected of being plugged or restricted, it must be re-
placed .
CAUSES OF HIGH LINE PRESSURE
a. Full leak (vacuum line disconnected) .
b. Partial leak in line from engine modulator.
d. Vacuum operated accessory leak . (Hoses,
vacuum advance, etc .) .
d. Orifice at end of modulator valve sleeve
plugged or not drilled .
a. Detent switch actuated (plunger stuck) or
shorted.
c. Detent solenoid valve stuck open . Solenoid
cover may be bent causing solenoid valve to be open .
d. Detent feed orifice in spacer plate blocked.
e. Detent solenoid loose.
f. Detent valve bore plug damaged.
g. Detent regulator valve pin short.
4. Pump .