GMC 1976 ZEO 6083 Maintenance Manual page 460

7- 12 TRANSMISSION
2. Oil cooler pipe connections not tight. Tighten
to 20 foot-pounds.
3. Flare on oil cooler pipes damaged at radiator
or transmission .
FILLER PIPE
1 . O-ring damaged or improperly installed on
pipe .
2. Filler Pipe not fully seated in case .
INTERNAL LEAKS
It will be necessary to remove bottom pan to
determine location of internal leaks.
1 . Governor pipes damaged.
2 . Control valve assembly-to-spacer or case gas-
kets damaged.
3. Control valve assembly attaching screws loose.
Tighten to 8 foot-pounds .
4. Solenoid gaskets damaged.
5. Solenoid attaching screws loose. Tighten to 8
foot-pounds.
6. Intake pipe O-ring damaged.
7. Rear servo square cut O-ring improperly in-
stalled or damaged.
FUNCTIONAL DIAGNOSIS
PROCEDURE
Dependability of the diagnosis charts depends
upon:
1 . Careful analysis of symptoms so that proper
malfunction on the charts will be used .
2 . Accurate oil pressure check with accurate
gauge is made as indicated on the chart and these
readings recorded so that they can be compared with
the diagnosis chart.
3 . Oil pressure readings must be made with trans-
mission oil at normal operating temperatures .
4. Refer to detailed diagnosis charts for addi-
tional diagnosis on 1-2 and 2-3 shift malfunction
diagnosis.
5 . Engine must be properly tuned to specifica-
tions .
ROAD TEST
Check All Shifts In The Following Manner :
DRIVE RANGE :
Position selector lever in DRIVE RANGE and
accelerate the vehicle from 0 mph. A 1-2 and 2-3
shift should occur at all throttle openings . (The shift
points will vary with the throttle opening) . As the
vehicle decreases in speed to 0 mph, the 3-2 and 2-1
shifts should occur.
SUPER RANGE:
Position the selector lever in SUPER RANGE
and accelerate the vehicle from 0 mph. A 1-2 shift
should occur at all throttle openings . (No 2-3 shift
can be obtained in this range) . The 1-2 shift point will
vary with throttle opening. As the vehicle decreases
in speed to 0 mph, a 2-1 shift should occur. NOTE :
The 1-2 shift in SUPER RANGE is somewhat
firmer than in DRIVE RANGE . This is normal .
LO RANGE:
Position the selector lever in LO RANGE and
accelerate the vehicle from 0 mph. No upshift should
occur in this range, except in some vehicles which
have a high numerical axle ratio and/or high engine
rpm.
2ND GEAR - OVERRUN BRAKING :
Position the selector lever in DRIVE RANGE,
and with the vehicle speed at approximately 35 mph,
move the selector lever to SUPER RANGE. The
transmission should downshift to 2nd. An increase in
engine rpm and an engine braking effect should be
noticed . Line pressure should change from approxi-
mately 70 psi to approximately 150 psi in 2nd .
1st GEAR - OVERRUN BRAKING :
Position the selector lever in SUPER RANGE at
approximately 30 to 40 mph, with throttle closed,
move the selector lever to Lo. A 2-1 downshift
should occur in the speed range of approximately 40
to 20 mph, depending on axle ratio and valve body
calibration. The 2-1 downshift at closed throttle will
be accompanied by increased engine rpm and an
engine braking effect should be noticed. Line pres-
sure should be approximately 150 psi. Stop vehicle.
REVERSE RANGE:
Position the selector lever in REVERSE POSI-
TION and check for reverse operation.