Chrysler Concorde 1993, Руководство по обслуживанию, Страница: 602 / 820

and ball valves are used. These are free from any
close operating clearances, and the solenoids operate
the valves directly. Direct operation means that
these units must have very high output so that they
can close against the sizeable flow areas and high
line pressures. Fast response is also required to meet
the control requirements.
Two of the solenoids are normally-venting and two
are normally-applying; this was done to provide a de-
fault mode of operation. With no electrical power, the
transmission provides 2nd gear in ‘‘OD,’’ ‘‘3,’’ or ‘‘L’’
shift lever positions. All other shift lever positions
will function normally. The choice of 2nd gear was
made to provide adequate performance while still ac-
commodating highway speeds.
SENSORS
There are three pressure switches which identify
solenoid application. The pressure switches are incor-
porated in an assembly with the solenoids. Two speed
sensors read input (torque converter turbine) and
output (parking sprag) speeds. There is also a man-
ual valve lever position sensor (MVLPS) which
senses manual valve position.
Engine speed, throttle position, temperature, etc.,
are also observed. Some of these signals are read di-
rectly from the engine control sensors; others are
read from a multiplex circuit with the engine con-
troller.
ADAPTIVE CONTROLS
These controls function by reading the input and
output speeds over 140 times a second and respond-
ing to each new reading. This provides the friction
element control needed to make smooth clutch-to-
clutch shifts for all gear changes without the use of
overrunning clutches. As with most automatic tran-
saxles, all shifts involve releasing one element and
applying a different element. In simplified terms, the
upshift logic allows the releasing element to slip
backwards slightly to ensure that it does not have
excess capacity; the apply element is filled until it
begins to make the speed change to the higher gear;
its apply pressure is then controlled to maintain the
desired rate of speed change until the shift is com-
plete. The key to providing excellent shift quality is
precision; for example, as mentioned, the release ele-
ment for upshifts is allowed to slip backwards
slightly; the amount of that slip is typically less than
a total of 20 degrees. To achieve that precision, the
transmission control module learns the characteris-
tics of the particular transaxle that it is controlling.
It learns:
•
The release rate of the releasing element.
•
The apply time of the applying element.
•
The rate the apply element builds pressure.
This method achieves more precision than would be
possible with exacting tolerances. It can also adapt to
any changes that occur with age or environment.
For kickdown shifts, the control logic allows the re-
leasing element to slip and then controls the rate at
which the input (and engine) accelerate; when the
lower gear speed is achieved, the releasing element
reapplies to maintain that speed until the apply ele-
ment is filled. This provides quick response and a
smooth torque exchange since the release element
can control the rate of torque increase. This control
can make any powertrain feel more responsive with-
out increasing harshness.
Adaptive controls respond to input speed changes.
They compensate for changes in engine or friction el-
ement torque. This provide consistent shift quality
for the life of the transaxle.
DIAGNOSTICS
These controls also provide comprehensive, on-
board transaxle diagnostics. The information avail-
able can aid in transaxle diagnosis. For example,
apply element buildup rate indicates solenoid perfor-
mance. Also included are self-diagnostic functions
which allow the technician to test the electronic con-
trols. The transmission control module monitors its
critical functions, records any malfunctions, and the
number of engine starts since the last malfunction.
The technician can use this information in the event
of a customer complaint. Refer to the ‘‘42LE Tran-
saxle Diagnostic Procedure Manual.’’for specifics.
42LE GENERAL DIAGNOSIS
CAUTION: Before attempting any repair on the 42LE
Four Speed Automatic Transaxle, always check for
proper shift linkage adjustment. Also check for di-
agnostic trouble codes with the DRB II scan tool
and the ‘‘42LE Transaxle Diagnostic Procedure
Manual.’’
42LE automatic transaxle malfunctions may be
caused by these general conditions:
•
Poor engine performance
•
Improper adjustments
•
Hydraulic malfunctions
•
Mechanical malfunctions
•
Electronic malfunctions
When Diagnosing a problem always begin with re-
cording the complaint. The complaint should be de-
fined as specific as possible. Include the following
checks:
•
Temperature at occurrence (cold, hot, both)
•
Dynamic conditions (acceleration, deceleration, up-
shift, cornering)
•
Elements in use when condition occurs (what gear
is transaxle in during condition)
•
Road and weather conditions
TRANSAXLE 21 - 3