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.