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TURBO HYDRA-MATIC 2 5 0 TRANSMISSION
7A2-5
3. Scored governor bore.
MANUAL LINKAGE
Manual linkage adjustment and associated neutral start
switch are important from a safety standpoint. The neutral
start switch should be adjusted so that engine will start in
Park and Neutral positions only.
With selector lever in Park position, parking pawl should
freely engage and prevent vehicle from rolling. The pointer
on indicator quadrant should line up properly with range
indicators in all ranges.
ROAD TEST
Drive Range
Position selector lever in DRIVE RANGE and
accelerate vehicle from 0 MPH. A 1-2 and 2-3 shift should
occur at all throttle openings (shift points will vary with
throttle opening). As vehicle decreases in speed to 0 MPH,
the 3-2 and 2-1 shifts should occur.
Low L2 Range
Position selector lever in L2 RANGE and accelerate
vehicle from 0 MPH. A 1-2 shift should occur at all throttle
openings (No. 2-3 shoft can be obtained in this range). The
1-2 shift point will vary with throttle opening. As vehicle
decreases in speed to 0 MPH, a 2-1 shift should occur.
The 1-2 shift in INTERMEDIATE (L2) RANGE is
somewhat firmer than in DRIVE RANGE. This is normal.
Low L1 Range
Position selector lever in L1 RANGE and accelerate
vehicle from 0 MPH. No upshift should occur in this range.
2nd Gear
-
Overrun Braking (L2 Range)
Position selector lever in DRIVE RANGE, and with
vehicle speed at approximately 35 MPH, move selector lever
to L2 RANGE: Transmission should downshift to 2nd. An
increase in engine RPM and an engine braking effect should
be noticed. Line pressure should change from approximately
55 PSI to approximately 125 PSI in 2nd.
1st Gear
-
Overrun Braking (L1 Range)
Position selector lever in L2 RANGE at approximately
30 to 50 MPH, with throttle closed, move selector lever to
L1. A 2-1 downshift should occur in speed range of
approximately 45 to 30 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 pressure should be
approximately 80 PSI. Stop vehicle.
Reverse Range
Position selector lever in REVERSE RANGE and check
for reverse operation.
TROUBLE DIAGNOSIS
Refer to Diagnosis Chart (Fig. 7A2-5) to determine a
possible cause of a transmission problem.
Additional diagnosis of a malfunction is as follows:
No Drive in Drive Range
(Install pressure gage)
Low Fluid Level
-
correct level and check for external
leaks or defective vacuum modulator (leaking diaphragm will
evacuate fluid from unit).
Manual Linkage
-
misadjusted, correct alignment to
manual lever shift quadrant is essential.
Low Fluid Pressure
-
refer to LOW LINE PRESSURE
below.
Forward Clutch:
a. Forward clutch does not apply, piston cracked
-
see
BURNED CLUTCH PLATES below.
b. Pump feed circuit-to-forward clutch oil seal rings
missing or broken on pump cover; leak in feed circuits; pump-
to-case gasket mispositioned or damaged; clutch drum ball
check stuck or missing.
Low and Reverse Roller Clutch Assembly
-
broken
spring, damaged cage or installed backwards.
High or Low Fluid Pressure
(Refer to FLUID PRESSURE CHECK)
High Line Pressure
Vacuum Leak:
a. Vacuum line disconnected.
b. Leak in line from engine to modulator.
c. Improper engine vacuum.
d. Leak in vacuum-operated accessory (hoses, vacuum
advance, etc.).
Modulator:
a. Stuck modulator valve.
b. Water in modulator.
c. Damaged, not operating properly.
Detent System
-
detent valve or cable stuck in detent
position.
Valve Body:
a. Pressure regulator and/or boost valve stuck.
b. Boost valve sleeve broken or defective.
c. Incorrect pressure regulator valve spring.
Low Line Pressure
Low transmission fluid 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:
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