Dodge Dakota (R1). Manual — part 624
OPERATION
Compensation is required for performance varia-
tions of two of the input devices. Though the slope of
the transfer functions is tightly controlled, offset may
vary due to various environmental factors or manu-
facturing tolerances.
The pressure transducer is affected by barometric
pressure as well as temperature. Calibration of the
zero pressure offset is required to compensate for
shifting output due to these factors.
Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absence
of sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the
9cold9 period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higher
than normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
sure curve is higher than normal to make the
transmission shift at normal speeds and sooner. The
PCM uses a temperature sensor in the transmission
oil sump to determine when low temperature gover-
nor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased
computing power of the PCM and through access to
data on engine operating conditions provided by the
PCM that were not available with the previous
stand-alone electronic module. This facilitated the
development of a load adaptive shift strategy - the
ability to alter the shift schedule in response to vehi-
cle load condition. One manifestation of this capabil-
ity is grade
9hunting9 prevention - the ability of the
transmission logic to delay an upshift on a grade if
the engine does not have sufficient power to main-
tain speed in the higher gear. The 3-2 downshift and
the potential for hunting between gears occurs with a
heavily loaded vehicle or on steep grades. When
hunting occurs, it is very objectionable because shifts
are frequent and accompanied by large changes in
noise and acceleration.
WIDE OPEN THROTTLE OPERATION
In wide-open throttle (WOT) mode, adaptive mem-
ory in the PCM assures that up-shifts occur at the
preprogrammed optimum speed. WOT operation is
determined from the throttle position sensor, which
is also a part of the emission control system. The ini-
tial setting for the WOT upshift is below the opti-
mum engine speed. As WOT shifts are repeated, the
PCM learns the time required to complete the shifts
by comparing the engine speed when the shifts occur
to the optimum speed. After each shift, the PCM
adjusts the shift point until the optimum speed is
reached. The PCM also considers vehicle loading,
grade and engine performance changes due to high
altitude in determining when to make WOT shifts. It
does this by measuring vehicle and engine accelera-
tion and then factoring in the shift time.
21 - 140
AUTOMATIC TRANSMISSION - 42RE
AN
ELECTRONIC GOVERNOR (Continued)
TRANSFER CASE LOW RANGE OPERATION
On four-wheel drive vehicles operating in low
range, the engine can accelerate to its peak more
rapidly than in Normal range, resulting in delayed
shifts and undesirable engine
9flare.9 The low range
governor pressure curve is also higher than normal
to initiate upshifts sooner. The PCM compares elec-
tronic vehicle speed signal used by the speedometer
to the transmission output shaft speed signal to
determine when the transfer case is in low range.
REMOVAL
(1) Hoist and support vehicle on safety stands.
(2) Remove transmission fluid pan and filter.
(3) Disengage wire connectors from pressure sen-
sor and solenoid (Fig. 69).
(4) Remove
screws
holding
pressure
solenoid
retainer to governor body.
(5) Separate solenoid retainer from governor (Fig.
70).
(6) Pull solenoid from governor body (Fig. 71).
(7) Pull pressure sensor from governor body.
(8) Remove bolts holding governor body to valve
body.
(9) Separate governor body from valve body (Fig.
72).
(10) Remove governor body gasket.
INSTALLATION
Before installing the pressure sensor and solenoid
in the governor body, replace o-ring seals, clean the
gasket surfaces and replace gasket.
(1) Place gasket in position on back of governor
body (Fig. 73).
(2) Place governor body in position on valve body.
Fig. 69 Governor Solenoid And Pressure Sensor
1 - PRESSURE SENSOR
2 - PRESSURE SOLENOID
3 - GOVERNOR
Fig. 70 Pressure Solenoid Retainer
1 - PRESSURE SOLENOID RETAINER
2 - GOVERNOR
Fig. 71 Pressure Solenoid and O-ring
1 - PRESSURE SOLENOID
2 - O-RING
3 - GOVERNOR
AN
AUTOMATIC TRANSMISSION - 42RE
21 - 141
ELECTRONIC GOVERNOR (Continued)
(3) Install bolts to hold governor body to valve
body.
(4) Lubricate o-ring on pressure sensor with trans-
mission fluid.
(5) Align pressure sensor to bore in governor body.
(6) Push pressure sensor into governor body.
(7) Lubricate o-ring, on pressure solenoid, with
transmission fluid.
(8) Align pressure solenoid to bore in governor
body (Fig. 74).
(9) Push solenoid into governor body.
(10) Place solenoid retainer in position on governor
(Fig. 75).
(11) Install
screws
to
hold
pressure
solenoid
retainer to governor body.
(12) Engage wire connectors into pressure sensor
and solenoid (Fig. 76).
(13) Install transmission fluid pan and (new) filter.
(14) Lower vehicle and road test to verify repair.
Fig. 72 Governor Body and Gasket
1 - GOVERNOR BODY
2 - GASKET
Fig. 73 Governor Body and Gasket
1 - GOVERNOR BODY
2 - GASKET
Fig. 74 Pressure Solenoid and O-ring
1 - PRESSURE SOLENOID
2 - O-RING
3 - GOVERNOR
Fig. 75 Pressure Solenoid Retainer
1 - PRESSURE SOLENOID RETAINER
2 - GOVERNOR
21 - 142
AUTOMATIC TRANSMISSION - 42RE
AN
ELECTRONIC GOVERNOR (Continued)
EXTENSION HOUSING
BUSHING
REMOVAL
(1) Remove extension housing yoke seal.
(2) Insert Remover 6957 into the extension hous-
ing. Tighten tool to bushing and remove bushing
(Fig. 77).
INSTALLATION
(1) Align bushing oil hole with oil slot in extension
housing.
(2) Tap bushing into place with Installer 6951 and
Handle C-4171.
(3) Install new oil seal in housing using Seal
Installer C-3995-A (Fig. 78).
EXTENSION HOUSING SEAL
REMOVAL
(1) Raise vehicle.
(2) Mark propeller shaft and axle yoke, or compan-
ion flange, for alignment reference.
(3) Disconnect and remove propeller shaft.
(4) Remove old seal with Seal Remover C-3985-B
(Fig. 79) from overdrive extension housing.
Fig. 76 Governor Solenoid And Pressure Sensor
1 - PRESSURE SENSOR
2 - PRESSURE SOLENOID
3 - GOVERNOR
Fig. 77 Bushing Removal - Typical
1 - REMOVER
2 - EXTENSION HOUSING BUSHING
Fig. 78 Extension Housing Seal Installation
1 - SPECIAL TOOL C-3995-A OR C-3972-A
2 - SPECIAL TOOL C-4471
Fig. 79 Removing Transmission Housing Yoke Seal
1 - SPECIAL TOOL C-3985-B
2 - SEAL
AN
AUTOMATIC TRANSMISSION - 42RE
21 - 143
ELECTRONIC GOVERNOR (Continued)
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