1988 PONTIAC FIERO transmission

HYDRAULIC DIAGNOSIS 700.R4-21
PARK- ENGlNE RUNNING
CONVERTER CLUTCH - RELEASED 34 CLUTCH - RELEASED 2.4 MUD - RELEASE0
REVERSE INPUT CLUTCH - RELEASED LO AND REVERIE CLUTCH - RELEASED OVERRUN CLUTCH - RELEASE0
FORWARD WUTCH - RELEASED LO ROUM CLUfCH - NOT HOLOlWO FORWARD SPRAQ CLUTCH - NaT HOLDIIYG
With the selector lever in the Park (PI position, oil from the pump is directed to the following:
1. Pressure Regulator Valve
2. Releasg Side of the Converter and the Lubrication System
3, Decrease Side of the Pump Slide
4. Manual Valve
5. T.V. System (Limit Valve, Throttle Valve, Line Bias Valve, M.T.V. Up Valve and M.T.V. Down Valve)
6. Pressure Relief Valve
7. Line Pressure Tap
Oil
flows from the pump to the pressure regulator vatve which regulates the pump pressure. When
the pump output exceeds the demand of line pressure, oil from the pressure regulator valve is directed
to the converter clutch apply valve. The converter clutch apply valve directs oil to the release side
of the converter clutch. Converter return oil is directed to the transmission cooler by the converter
clutch
apply valve, Oil from the cooler is directed to the transmission lubrication system.
Oil is also directed from the pressure regulator valve to the pump slide to decrease pump output in
relation to the combined pressure of M.T.V. oil and regulator valve spring force. Line pressure acts
on the pressure relief valve which will exhaust any oil above 2,240 to 2,520 kPa (320 to 360 psi).
Line pressure at the manual valve is available for use in other drive ranges.
Line pressure at the T.V. limit valv~ is limited to 620 kPa (90 psi). This limited pressure is directed
to the throttle valve where it is regulated to a variable pressure called throttle valve (T.V,) pressurn
T.V. pressure increases with carburetor opening and is directed to the line bias, MXV. up and M.T.V.
down valves.
At the line bias valve, T.V. pressure is modulated to M.T.V. pressure. M.T.V. pressure helps to control
line pressure
at the pressure regulator valve and accumulator pressure at the sceumulator valve.
T.V, pressure at the M.T.V. up valve and M.T,V. down valve js available for use when accelerating in
other ranges.
SUMMARY
The convener is filled from the release side; all clutches and the band are released. The manual linkage
has the parking pawl engaged in the reaction internal gehr lugs. At idle, them is not sufficient T,V.
pressure to open the MXV, up or M.T.V. down vakes.
JHO176.7OOR4 1
Figure 18 Park - Engine Running

HYDRAULIC DIAGNOSIS 70064-2
FORWARD CLUTCH - APPLIED
D-4-FIRST GEAR
LO ROLLER CLUTCH - HOLDlllO FORWARO SPRRQ CLUTCH - HOLDING
When the selector lever is moved to the Orive {Dl position, the manual valve is repositioned to allow
line pressure to enter the Drive 4 104) passaga Drive 4 oil then flows to the following:
1. Forward Clutch Accumulator, Forward Clutch and Abuse Valve
2. Governor Valve
. 3. 1-2 Shift Valve
4, Accumulator Valve
5. 3-4 Shift Valve
BASIC CONTROL
Drive 4 oil is directed to the forward clutch accumulator where the #I2 checkball seats, routing
forward clutch feed through an orifice. This combines with the forward clutch accumuIator to cushion
the forward clutch
apply,
During "Rock Cyclea' cpnditions (stuck in mud or snow and "Rocking" out), an abuse valve routes
D4 oil to forward clutch feed oil to quicken the apply of the forward clutch.
Driw 4 oil is directed to the 1-2 and 3-4 shift valves, Drive 4 oil is directed to the accumulator valve
and is regulated to a pressure called accumulator pressure; this pressure is directed to the 1-2 and
3-4 accumulator pistons to act as a cushion for the band apply in second gear and overdrive.
'Drive
4 oil is orificed into the gwernor passage, and is regulated to a variable pressure called governor
pressure. Governor pressure increases with vehicle speed and acts against the 1-2, 2-3, 3-4, con-
verter clutch and the 3-2 control valve springs.
In first gear, there could
be sufficient throttle valve plunger travel to increase T.V. pressure enough
to open the MW. up and the M.T.V. down valves. In first gear, MXV. up exerts pressure against governor
pressure at the 1-2, 2-3, 3-4, and converter clutch throttle valves. M.T.V. down pressure is stopped
by a land at the 2-3 and 34 throttle valves,
SUMMARY
The converter clutch is released, the forward sprag dutch is holding, the forward clutch is applied;
the transmission is i'n Drive (Dl Range - First Gear.
I Jn0177-700M Figure 22 D4 - First Gsar

HYDRAULIC PlAONOSlS fOO-R4-27
D-4-SECOND GEAR
FORWARD SPRAE CLUTCH - HOLDlMO 24 BAND - APPLIED FOIWARD CLUTCH - APPLIEP
As both vehicle speed and govanor pressure increase, the force of the governor oil acting on the 1-2
shift valve overcomes the pressure of M.T.V. up oil and the force of the 1-2 throttle valve spring. This
allows the 1-2 shift valve to open and Drive 4 (041 oil to enter the second (2nd) oil passage. This
oil is called second (2nd) oil. Second oil from the 1-2 shift valve is directed to the following:
1. 1-2 Shift Checkbatl (8)
2, 2-4 Servo
3. 1-2 Accumulator Piston
4. Converter Clutch Shift Valve
5. 3-4 Relay Valve
WlC CONTROL
Second ail from the 1-2 shift valve will seat the 1-2 shift checkball (8) forcing 2nd oil through an orifice.
Second oil Is then directed to the 2-4 servo to apply the 2-4 band. At the same time, 2nd oil moves
the 1-2 eccumulator piston against accumulator pressure and the accumulator spring to maintain a
controlled build-up of pressure on the servo during tho 1-2 shift for a smooth bend apply 2nd oil at
the converter clutch shift vatve and the 3-4 relay valve is availabl~ for use in other ranges.
SUMMARY
The converter clutch is released, the 2-4 band is applied, the forward clutch is applied, and the for-
ward spmg clutch is holding; the transmission is in Drive (Dl Range - Second Gear,
dH017B.7OOR4 -
Figure 24 D4 - Second Gear

HYDRAULIC DfAQNOSIS 70044-31
As both vehicle speed and governor pressure increase, the force of gowrnor oil acting on the 2-3
shift valve overcomes the force of the 2-3 T.V. spring and MXV. up oil, This allows the 2-3 shift valve
to
open and allows RN04D3 oil to enter the 3rd clutch passage.
Third clutch oil from the 2-3 shift valve is directed to the following:
1. 3-2 Exhaust Checkball (4)
2. 3-4 Clutch Piston
3. Third Clutch Accumulator Checkball (2)
4. Third Accumulator Exhaust: Checkball (7)
6. 2-4 Servo 1Release Side)
6. 3-2 Control Valve
D-4-THIRD GEAR
[Converter CItPtch Applied)
COMVERTER CtUTCli - APPLIED FOAWARD CLUTCH - APPLIED
FORWARD SFRAG CLU7CH - HPLDINO 34 CLUTCH - APPLIED
Third clutch oil from the 2-3 shift valve flows past the 3-2 exhaust checkball (4), to the 3-4 clutch
piston. At the same time, third clutch oil is directed past the third clutch accumulator checkball {2),
seats the third accumula'tor exhaust check ball (71, and then into the release side of the 2-4 serva
This third clutch accumulator pressure combined with the servo cushion spring, moves the second
apply piston, in the 2-4 servo, against second oil and acts as an accumulator for a smooth 2-4 band
release and 3-4 clutch apply.
Third clutch oil is present at the 3-2 control valve In preparation of a third gear to second gear shift.
Once the solenoid teceives a signal from the vehicles controls and solenoid is on, convefier clutch
signal oil will shift the converter clutch apply valve, and redirect converter feed oil into the apply passage.
the apply oil flows between the stator shaft and converter hub to charge the converter with oil and
push the converter pressure plate against the converter cwer, causing a mechanical link between
the engine and the turbhe shaft. The rate of apply is controlled by the orifice checkball capsule in
tha end of the turbine shaft.
At tho same time the converter clutch appfy valve will direct converter feed oil through an orifice to
the transmission cooler. Cooler oil is directed to the transmission lubrication sysm.
SUMMARY
The converter clutch is applied*, the forward clutch is applied, tho forward sprag clutch is holding,
the 3-4 clutch is applied and the 2-4 band is released; the transmission is in Drive (Dl Range - Third
Gear (direct drive).
+The converter clwh msy or may not be applied, depending on Aitt calibration and salenoid operation. JHOI 80+7OOA4
Figure 28 D4 - Third Gear - Converter Clutch Applkd

D-4- OVERDRIVE
HYDRAUUC DIAGNOSIS 70044-33
CONVERTER CLUTCH - APPLIED 9-4 CLUKH - APPLIED 24 3AlD - APPLIED
FORWARO CLUTCH - APPLIED FORWARD SPRM CLUTCH - HOT HOLDlNO
As both vehlcle speed and governor pressure incwaae, the force of governor oil acting on the 3-4
shift valve overcomes the force of the 3-4 T.V, spring and M.T.V. up oil. This opens the 3-4 shift valve
sending Drive 4 lD41 into the fourth signal passage. Fourth signal oil will overcome the 4-3 sequence
valve spring and open the 3-4 relay and the 4-3 sequence valves, allowing second oil to enter the
servo feed passage.
Servo feed oil is directed to the following:
1. 2-3 Shift Valve
a. Which directs oil to the:
1) 3-4 Accurnuiator
2) 4-3 Sequence Valve
2. 4-3 Sequence hive
a. Which directs oil to the:
1) 4th Apply Piston (in the 2-4 servo)
SUMMARY
The converter clutch, 24 band, forward clutch, the 3-4 clutch an applied, and the forward sprag
clutch is werrunning; the transmission is in Drive (D) Range - Overdrive,
*Tha converter clutch may or may not ba applied, depending on denoid operation.
JHOI er.?ow
Figure 30 b4 - Overdrive
BASIC CONTROL
Servo feed oil passes through the 4-3 sequence valve and becomes fourth oil. Fourth oil then enters
the
2-4 servo, applies pressure on the fourth apply piston, and applles the 2-4 band.

HYDRAULIC DIAGNOSIS 7004437
COIYVEIWER CLUTCH - RELEASED
FORWARD CLUltH - APPUEO
DETENT DOWNSHIFTS
1Valves In Second Gear Position)
2.4 BAND - APPLIED
FORWARD
SPRAQ CLUTCH - HOLDING
While operating at speeds below approximately 60 mph (96 kmth), a forced or detent 3-2 downshift
is possible by dapressing the accelerator pedal fully. This will position the throttle valve {T.V.}
plunger to allow T.V. oil to enter the detent passage. This oil, called detent oil, is then routed to
the following:
I. Line Bias Valve
2. 2-3 Throttle Valve
3. 1-2 Throttle Valve
4. Converter Clutch Throttle Valve (Non EC.M. Controlled Vehicles Only}
Detent ail from the T.V. plunger flows to the line bias valve to boost modulated T.V. (M.T.V.1 pressure.
M.T.V. oil acting on the T.V. boost valve will boost line pressure approximately 70 kPa (10 psi).
NON E.C.M. CONTROLLED VEHICLES
Detent oil at the cmverter clutch throttle valve will close the converter clutch shift valve train and
release the converter clutch.
E.C.M. CONTROLLED VEHCLES
The E.C.M. wll discontinue the signal provided to the solenoid to release the converter ctutch.
Dstent oil from the 7.V. plunger flows to the 2-3 throttle valve. Detent and M.T.V. down ol, acting
on separate
areas of the 2-3 throttle valve, will close the 2-3 shift valve against governor oil and allow
3rd clutch and 3rd accumulator oil to pass through an orifice and exhaust at the 2-3 shift valve.
At vehicle speeds above approximately 50 rnph (80 km/h), governor oil acting on the 3-2 control valve
will close it. Now the exhausting 3rd clutch accumulator oil from the inxemediate servo will seat the
3rd clutch accumulator checkball
(21 and low through another orifi~e controlling the intermediate
band apply for
a smooth 3-2 shift at high speed.
A detsnt 2-1 downshift can be accomplished at speeds below approximately 30 mph 148 krnlh),
because detent oil pressure and the 1-2 spring force acting on the 1-2 throttle valve will close the
1-2 shift valve, shifting the transmission to first gear.
JH018S-700A4
Figure 34 Deterit Downshifts

HYDRAULIC DIAGNOSIS 70044-39
MANUAL THIRD
CONVERTER CLUTCH - RELEASED
FORWARD CLUTCH - APPLIED
OVERRUN CLUTCH - APPUED
3.4 CLUfeH - APPLIEP
A forced 4-3 downshift can be accomplished by moving the selector lever from Drive 10) Range to
Third {3rd) Gear. When the selector lever is moved to the Third (3rd) Gear position, 03 oil from the
manual
valve is directed to the following:
1. 4-3 Sequence Valve
2. Part Throttle and Drive 3 103) Checkball 131
3. 3-4 Shift Valve
03 oil will close the 34 shift valve and allow the 4th signal oil to exhaust.
D3 oil combined with the 4-3 sequence valve spring force will close the 4-3 sequence valve to allow
the fourth and fourth accumulator oil to exhaust and release the band. 03 oil then flows into the over-
run clutch passage where it applies the overrun clutch to keep the forward sprag clutch from over-
running when engine braking is n~eded.
The forward and 3-4 CIU~C~~S are applied. The 2-4 band is released. The transmission is in Manual
Third,
direct driva The overrun clutch is appRad to allow engine braking.
*NON E,C.M, CONTROLLED VEHICLES
In manual 3td, the converter is shown released by the engine vacuum switch and there is no M.T.V.
up or M.T.V. down pressure, This is assuming the throttle is released. If the throttle is opened
sufficiently, the converter clutch could engage and the M.T.V. up and MXV. down valves coJd open.
JHOtOQ7WRI I
Figure 36 Manual Third

, HYDRAULIC PlAGNQSlS 7004441
MANUAL SECOND
COWERTER CLUTCH - RELEASED
OVEARUN CLUTCH - APPLIED
2.4 MUD - APPLIED
I
FORWARD CLUTCH - APPLIED
I
A forced 3-2 downshift cen be a~cornplished by moving the selector lever from Third (3rd) Gear to
Second (2nd) Gear position.
When
the selector lever is moved to the Second (2nd) Gear position, RND4D3, 3rd clutch, and 3rd
accumulator oil
will exhaust at the manual valve, With no pressure to apply the 34 clutch, or release
the 2-4 band, the transmission will shift to second gear.
The manual valve will also direct line pressure into the D2 passage, Drive 2 (D2) oil will act on the
reverse boost valve to boost line pressure to 1206 kPa (I75 psi) which is required to prevent the 2-4
band and forward clutch from slipping.
SUMMARY
The forward clutch and 2-4 band are applied. The transmission is in second gear. Also, the werrun
clutch is still applied to allow engine braking when needed.
JHOlUWOOR4 1
Figure 38 Manual Se~ond