Mitsubishi Eclipse. Technical Information Manual (1994) — part 42
POWER TRAIN
Automatic Transaxle
Body Assembly
Retainer
Valves removed
Valves installed
The
has a relatively simple, cast aluminum
valve body that uses only five valves. No governor
pressure or throttle pressure is used to operate
this valve body. These two pressures have been
replaced by electronic signals from the output speed
sensor and throttle position sensor. Shift valves have
and to direct fluid to the clutches, torque converter,
lubrication system, and the solenoid/valves by
means of the manual and switch valves.
One side of the rooster comb (secured to top of
valve body) operates two switches, the park neutral
also been eliminated and replaced by the solenoid/
and transmission range switches. The solenoid and
valves in the solenoid assembly.
pressure switch assembly is indirectly connected
The valve body has two major functions. To control
to the valve body through an extension of the case
line pressure and torque converter clutch pressure
in the oil pan area.
Solenoid and
pressure switch
assembly
Screen
filter
Solenoid and Pressure Switch Assembly
The solenoid and pressure switch assembly is controlled by
the TCM through the transmission control relay. The assembly
consists of four solenoid/valve assemblies that control hydraulic
pressure to four of the five clutches in the transaxle and the
torque converter clutch. A unique feature of the solenoid/valves
are that they directly control the application of a clutch. In
other electronically controlled
the
clutches are indirectly controlled by the solenoids through the
normal hydraulic valving. The solenoid assembly also contains
three pressure switches that feed information to the TCM. The
“UR” pressure switch, the “2-4” pressure switch and the
pressure switch. The eight-way electrical connector to the sole-
noid is sealed and bolted in place with the bolt tightened to
proper specification.
The assembly is located outside the transaxle case, under
a sound shield and protective cover, towards the front of the
vehicle. The filter screen between the solenoid assembly and
valve body protects the assembly from contamination and is
a replaceable item. However, if the valve body and solenoid
pack have been heavily contaminated, the solenoid pack should
be closely inspected to determine the need for its replacement.
The solenoid pack is not a serviceable unit.
POWER TRAIN
Automatic Transaxle
2-55
Torque converter
control valve
Overdrive clutch
Solenoid
Pump (IN)
1
Regulator Valve
The regulator valve has one function, to regulate or control
hydraulic pressure in the transaxle. The pump supplies unregu-
lated pressure to the regulator valve. The regulator valve con-
trols or limits pump pressure. Regulated pressure is referred
to as “line pressure”. The regulator valve has a spring on one
end that pushes the valve to the right. This closes a dump
(vent) to lower pressure. Closing the dump will cause oil pres-
sure to increase. Oil pressure on the opposite end of the valve
pushes the valve to the left, opening the dump and lowering
oil pressure. The result is spring tension working against oil
pressure to keep or maintain the oil at specific pressures. Regu-
lated pressure will vary depending on the gear range the trans-
axle is operating in.
A system of sleeves and ports allows the regulator valve to
work at one of three different predetermined pressure levels.
The oil that is dumped by the regulator valve is directed back
to the intake side of the oil pump.
Torque Converter Control Valve
The main responsibility of the torque converter (T/C) control
valve is to control hydraulic pressure applied to the front (“off”)
side of the converter clutch (CC). Line pressure from the regula-
tor valve is fed to the T/C control valve where it passes through
the valve. The T/C control valve reduces or regulates the pres-
sure slightly. The T/C control valve pressure is then directed
to the converter clutch (CC) control valve and to the front
side of the converter clutch piston.
The pressure that is being fed to the front of the piston pushes
the piston back. This disengages the converter clutch. The
oil then passes around the outside of the piston, flowing out
of the torque converter and back to the T/C control valve.
From the T/C control valve the oil flows to the transaxle oil
cooler and cooler bypass valve. It returns to the transaxle
as lube oil pressure.
2-56
POWER TRAIN - Automatic Transaxle
valve
From manual valve
Line
pressure
clutch
Solenoid
CLUTCH
e n e r g i z e d
t
valve
Solenoide
de-energized
clutch
t
II
pressure
pressure
switch
switch
Manual
valve
Manual
valve
clutch
Converter Clutch Control Valve
The CC control valve has the job of controlling the back or
“on” side of the torque converter clutch. When the TCM ener-
gizes the
solenoid to engage the converter clutch piston,
the CC control valve and T/C control valves move to the left.
The oil on the front or “off” side of the converter clutch piston
is vented to the sump.
Line pressure enters the CC control valve through the manual
valve and then passes through the CC control valve and the
T/C control valve to the back (“on”) side of the converter clutch
piston. Line pressure forces the piston forward which engages
the torque converter clutch. This action effectively connects
the torque converter turbine with the impeller. Line pressure
also flows from the regulator valve, through the T/C control
valve, to the cooler and cooler bypass for improved fluid and
transaxle cooling.
Solenoid Switch Valve
The switch valve controls line pressure direction from the
solenoid. When the valve is shifted to the right, it allows the
low/reverse (L/R) clutch to be pressurized. When it is shifted
to the left, it directs line pressure to the T/C and CC control
valves to operate the T/C clutch. The valve is shifted to the
right in all positions except second, third, or fourth gear. When
the transaxle upshifts to second gear, the valve moves to the
left which allows converter clutch engagement when needed.
The valve must return to the right before a downshift to first
gear can occur.
POWER TRAIN
Automatic Transaxle
valve
Solenoid
switch
valve
Vent to
sump
I
Overdrive
Manual Manual
valve
valve
(de-ene rgized)
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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