Pontiac FIREBIRD 1972 Service Manual page 1043

TURBO HYDRA-MATIC (M-38) TRANSMISSION 7G-5
LOW LINE PRESSURE
FIRST SPEED ONLY-NO 1-2 SHIFT
Low transmission oil level.
Defective vacuum modulator assembly.
Strainer Assembly:
a. Blocked or restricted.
b. Gasket omitted or damaged.
Oil Pump:
a. Gear clearance, damaged, worn, gear installed
backwards.
b. Pump-to-case gasket mispositioned.
c. Defective pump body and/or cover.
Valve Body:
a. Pressure regulator or boost valve stuck.
b. Pressure regulator valve spring, too weak.
Internal Circuit Leaks:
a. Forward clutch leak (pressure low in Drive range,
pressure normal in Neutral and Reverse).
(1) Check pump oil seal rings.
(2) Check forward clutch seals.
b. Direct clutch leak (pressure low in Reverse, pres-
sure normal in other ranges).
(1) Check direct clutch outer seal.
(2) Check 1-2 accumulator and 2-3 accumulator
pistons and rings for damage or missing.
Case Assembly
-
check ball missing from cored pas-
sage in case face.
1-2 SHIFT
-
FULL THROTTLE ONLY
1. Detent Valve
-
sticking or linkage misadjusted.
2. Vacuum Leak
-
vacuum line or fittings leaking.
3. Control Valve Assembly:
a. Valve body gaskets
-
leaking, damaged or incor-
rectly installed.
b. Detent valve train stuck.
c. 1-2 valve stuck closed (in downshifted position).
4. Case Assembly
-
porosity*.
1. Detent (downshift) cable
-
binding.
2. Governor Assembly:
a. Governor valve sticking.
b. Driven gear loose, damaged or worn (check for
pin in case and length of pin showing; also, check
output shaft drive gear for nicks or rough finish
if driven gear shows damage).
3. Control Valve Assembly:
a. Valve body gaskets
-
leaking, damaged or incor-
rectly installed.
b. Governor feed channels blocked.
c. 1-2 shift valve train stuck closed (in downshifted
position).
4. Intermediate Clutch:
a. Clutch piston seals
-
missing, improperly installed
or cut.
b. Intermediate roller clutch
-
broken spring or da-
maged cage.
5. Case:
a. Porosity* between channels.
b. Governor feed channel blocked; governor bore
scored or worn, allowing cross pressure leak.
FIRST AND SECOND SPEEDS ONLY-NO
2-3 SHIFT
1. Control Valve Assembly:
a. Valve body gaskets
-
leaking, damaged or incor-
rectly installed.
b. 2-3 shift valve train stuck closed (in downshifted
position).
2. Direct Clutch:
a. Pump hub
-
direct clutch oil seal rings
-
broken
or missing.
b. Clutch piston seals
-
missing, improperly assem-
bled or cut.
c. Clutch plates burned (see BURNED CLUTCH
PLATES below).