Pontiac Fiero 1988 Service Manual page 743

125C-2 HYDRAULIC DIAGNOSIS
• 4-element hydraulic torque converter
• Compound planetary gear set
• Dual sprocket and drive link assembly
m Three multiple disc clutches
• One roller clutch
• Intermediate band assembly
• Valve body assembly
• Vane type oil pump
The oil pressure and shift points are controlled by
throttle opening via a throttle valve cable (See the 7A
section for T.V. cable information).
The transaxle can be operated in any of six
different modes shown on the shift quadrant.
P- Park position prevents the vehicle from
rolling either forward or backward. (For safety reasons
the parking brake should be used in addition to the
park position.)
R- Reverse allows the vehicle to be operated in
a rearward direction.
N- Neutral allows the engine to be started and
operated without driving the vehicle. If necessary this
position may be selected if the engine must be restarted
with the vehicle moving.
D- Drive position is used for all normal driving
conditions. It provides three gear ratios plus converter
clutch operation. Downshifts are available for safe
passing by depressing the accelerator.
2 - Manual second is used to provide acceleration
and engine braking. This range may be selected at any
vehicle speed.
1- Manual Lo is used to provide maximum
engine braking. This range may also be selected at any
vehicle speed.
DIAGNOSIS INFORMATION
ROAD TEST PROCEDURE
• Perform the road test following the sequence
given
® MPH (KPH) shift points will vary with actual
throttle position and driver habits
• Compare the results of the test with speed shift
chart information. Use these results with the
diagnosis information in the specific Automatic
Transaxle Unit Repair Section to evaluate the
transaxle.
m This test should only be performed when traffic
and road conditions permit
• Observe all traffic safety regulations
Garage Shift Check
1. Start engine
2. Depress brake pedal
3. Move gear selector:
- "Park" (P) to "Reserve
55
(R)
- "Reverse
55
(R) to "Neutral
55
(N) to "Drive
55
(D)
Gear selections should be immediate and
not harsh.
Upshifts and Torque Converter Clutch (TCC)
Apply (Figure 2)
With gear selector in "Drive
55
(D)
1. Accelerate using a steady increasing throttle
pressure
2. Note the shift speed point gear engagements for:
2nd gear
3rd gear
3. Note the speed shift point for TCC apply. This
should occur between 15 - 25 MPH (24 - 40
KPH). If the apply is not noticed, refer to the
Preliminary Torque Converter Clutch Diagnosis
information contained in this section of the
Service Manual.
Important
The torque converter clutch will not engage if
engine coolant has not reached a minimum
operating temperature of approximately 5 4 ° C
(130°F).
Part Throttle Detent Downshift
At
vehicle
speeds of 25-55 MPH (40-88
KPH) quickly depress the accelerator to a
half open position and observe:
TCC releases
- Transaxle downshift to 2nd gear
immediately
Full Throttle Detent Downshift
At
vehicle
speeds of 25-55 MPH (40-88
KPH) quickly depress the accelerator to a
wide open position and observe:
TCC releases
Transaxle downshifts to 2nd gear
immediately
Manual Downshift
1.
At vehicle
speeds
of 25-55 MPH (40 to
88
KPH)
release the accelerator pedal while moving the
gear selector to "Second
55
gear (2) and observe:
TCC release
Transaxle downshift to 2nd gear should be
immediate
Engine should slow vehicle down
2. Move gear selector to "Drive
55
(D) and accelerate
to 25 MPH (40 KPH). Release the accelerator
pedal while moving the gear selector to "First
55
gear (1) and observe:
- TCC release
Transaxle downshift to 1st gear should be
immediate
Engine should slow vehicle down
Coastdown Downshift
1. With the gear selector in "Drive
55
(D) accelerate
the vehicle to 3rd gear with TCC applied.
2. Release the accelerator pedal and lightly apply