POWER TRAIN
-
Automatic Transaxle
2-57
UD
clutcn
valve
-
Solenoid
switch
valve
Vent to
mxgive
sump
4
/
+
hh
\mn,
1
Taaer
/
I.”
“rod
I
I
Overdrive
~~~~~~11,
3
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cllltnh
Manual Manual
-.
-
.-.
solenok
i
valve
valve
(de-energized)
Manual Valve
The manual valve is operated by mechanical shift linkage only.
Its job is to send line pressure to the appropriate hydraulic
circuits and solenoids. The valve has three operating ranges
or positions. The valve is shifted to the left position when Over-
drive (OD), Drive (3) or Low (L) is selected. The valve is shifted
to the middle position in both Park (P) and Neutral (N). The
valve is moved to the right position when Reverse (R) is se-
lected.
Low Reverse/Converter Clutch and Overdrive Solenoids
When these two solenoids are not energized by the TCM,
their check balls are seated on orifices and do not allow hydraulic
pressure to pass through their particular circuits. The top of
these solenoids are tapered to allow fluid to vent to the sump
when de-energized. They are referred to as normally vented
valves. When the solenoids are energized by the TCM, the
check balls are unseated, allowing hydraulic pressure to flow
past the check ball and into the circuit. At the same time,
the tapered part of the solenoid closes the vent port to the
sump. This action causes full line pressure to be applied to
the desired clutch.
The TCM can cycle (turn “on” and “off”) the solenoids at a
high frequency (many times per second). This action modulates
the element pressure between zero and line pressure. The
modulation is used when the solenoids are initially eneragized
for more precise control of the clutches. Under certain driving
conditions, the TCM may modulate the LWCC solenoid to
obtain a specific amount of T/C clutch slippage. This feature
is referred to as Electronically Modulated Converter Clutch
(EMCC). It allows partial converter clutch engagement, which
gives increased fuel economy and smoothes out engine pulses.
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