Jeep Wrangler TJ. Manual - part 512

The most common practice is to increase the num-

ber of turns by using thin wire that can completely
fill the available space within the solenoid housing.
The strength of the spring and the length of the
plunger also contribute to the response speed possi-
ble by a particular solenoid design.

A solenoid can also be described by the method by

which it is controlled. Some of the possibilities
include variable force, pulse-width modulated, con-
stant ON, or duty cycle. The variable force and pulse-
width modulated versions utilize similar methods to
control the current flow through the solenoid to posi-
tion the solenoid plunger at a desired position some-
where between full ON and full OFF. The constant
ON and duty cycled versions control the voltage
across the solenoid to allow either full flow or no flow
through the solenoid’s valve.

OPERATION

When an electrical current is applied to the sole-

noid coil, a magnetic field is created which produces
an attraction to the plunger, causing the plunger to
move and work against the spring pressure and the
load applied by the fluid the valve is controlling. The
plunger is normally directly attached to the valve
which it is to operate. When the current is removed
from the coil, the attraction is removed and the
plunger will return to its original position due to
spring pressure.

The plunger is made of a conductive material and

accomplishes this movement by providing a path for
the magnetic field to flow. By keeping the air gap
between the plunger and the coil to the minimum
necessary to allow free movement of the plunger, the
magnetic field is maximized.

SOLENOID/PRESSURE
SWITCH ASSY

DESCRIPTION

The Solenoid/Pressure Switch Assembly (1) (Fig.

238) is inside the transmission and mounted to the
valve body assembly. The assembly consists of four
solenoids that control hydraulic pressure to the L/R,
2/4, OD, and UD friction elements (transmission
clutches), and the torque converter clutch. The
reverse clutch is controlled by line pressure from the
manual valve in the valve body. The solenoids are
contained

within

the

Solenoid/Pressure

Switch

Assembly, and can only be serviced by replacing the
assembly.

The solenoid assembly also contains pressure

switches that monitor and send hydraulic circuit
information to the TCM. Likewise, the pressure
switches can only be service by replacing the assem-
bly.

Fig. 237 Low Reverse/Converter Clutch and

Overdrive Solenoids

1 - OVERDRIVE CLUTCH
2 - NO VENT
3 - OVERDRIVE SOLENOID ENERGIZED
4 - MANUAL VALVE
5 - LOW REVERSE/CONVERTER CLUTCH SOLENOID DE-
ENERGIZED
6 - SOLENOID SWITCH VALVE
7 - TAPER
8 - VENT TO SUMP
9 - ORIFICE
10 - CHECK BALL

Fig. 238 Valve Body Assembly

1 - SOLENOID/PRESSURE SWITCH ASSEMBLY
2 - TRS
3 - TRANSFER PLATE
4 - SEPARATOR PLATE
5 - VALVE BODY

21 - 138

AUTOMATIC TRANSMISSION - 42RLE

SOLENOID (Continued)

OPERATION

SOLENOIDS

The solenoids receive electrical power from the

Transmission Control Relay through a single wire.
The TCM energizes or operates the solenoids individ-
ually by grounding the return wire of the solenoid
needed. When a solenoid is energized, the solenoid
valve shifts, and a fluid passage is opened or closed
(vented or applied), depending on its default operat-
ing state. The result is an apply or release of a fric-
tional element.

The 2/4 and UD solenoids are normally applied,

which allows fluid to pass through in their relaxed or
“off” state. By design, this allows transmission
limp-in (P,R,N,2) in the event of an electrical failure.

The continuity of the solenoids and circuits are

periodically tested. Each solenoid is turned on or off
depending on its current state. An inductive spike
should be detected by the TCM during this test. If no
spike is detected, the circuit is tested again to verify
the failure. In addition to the periodic testing, the
solenoid circuits are tested if a speed ratio or pres-
sure switch error occurs.

PRESSURE SWITCHES

The TCM relies on three pressure switches to mon-

itor fluid pressure in the L/R, 2/4, and OD hydraulic
circuits. The primary purpose of these switches is to
help the TCM detect when clutch circuit hydraulic
failures occur. The range for the pressure switch clos-
ing and opening points is 11-23 psi. Typically the
switch opening point will be approximately one psi
lower than the closing point. For example, a switch
may close at 18 psi and open at 17 psi. The switches
are continuously monitored by the TCM for the cor-
rect states (open or closed) in each gear as shown in
the following chart:

PRESSURE SWITCH STATES

GEAR

L/R

2/4

P/N

1st

2nd

OP = OPEN

CL = CLOSED

A Diagnostic Trouble Code (DTC) will set if the

TCM senses any switch open or closed at the wrong
time in a given gear.

The TCM also tests the 2/4 and OD pressure

switches when they are normally off (OD and 2/4 are
tested in 1st gear, OD in 2nd gear, and 2/4 in 3rd
gear). The test simply verifies that they are opera-
tional, by looking for a closed state when the corre-
sponding element is applied. Immediately after a
shift into 1st, 2nd, or 3rd gear with the engine speed
above 1000 rpm, the TCM momentarily turns on ele-
ment pressure to the 2/4 and/or OD clutch circuits to
identify that the appropriate switch has closed. If it
doesn’t close, it is tested again. If the switch fails to
close the second time, the appropriate Diagnostic
Trouble Code (DTC) will set.

REMOVAL

NOTE: If the Solenoid/Pressure Switch Assembly is
being replaced, the Quick Learn Procedure must be
performed. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL

MODULES/TRANSMISSION

CONTROL

MODULE - STANDARD PROCEDURE)

(1) Raise vehicle on hoist.
(2) Remove valve body assembly from transmis-

sion. (Refer to 21 - TRANSMISSION/AUTOMATIC -
42RLE/VALVE BODY - REMOVAL)

(3) Remove

Solenoid/Pressure

Switch Assembly

retaining screws (2) from solenoid (Fig. 239).

Fig. 239 Solenoid Retaining Screws

1 - SOLENOID/PRESSURE SWITCH ASSEMBLY
2 - RETAINING SCREWS

AUTOMATIC TRANSMISSION - 42RLE

21 - 139

SOLENOID/PRESSURE SWITCH ASSY (Continued)

(4) Remove Solenoid/Pressure Switch Assembly (1)

and screen from valve body (2) (Fig. 240).

INSTALLATION

NOTE: If the Solenoid/Pressure Switch assembly is
being replaced, the Quick Learn Procedure must be
performed. (Refer to 8 - ELECTRICAL/ELECTRONIC
CONTROL

MODULES/TRANSMISSION

CONTROL

MODULE - STANDARD PROCEDURE)

(1) Install Solenoid/Pressure Switch Assembly (1)

(Fig. 241) and screen (3) to the separator and trans-
fer plates.

(2) Install and tighten retaining screws (2) (Fig.

242) to 5.5 N·m (50 in. lbs.) torque.

(3) Install valve body. (Refer to 21 - TRANSMIS-

SION/AUTOMATIC

42RLE/VALVE

BODY

INSTALLATION)

Fig. 240 Solenoid/Pressure Switch Assembly and

Screen

1 - SOLENOID/PRESSURE SWITCH ASSEMBLY
2 - VALVE BODY
3 - SCREEN

Fig. 241 Solenoid/Pressure Switch Assembly and

Screen

1 - SOLENOID/PRESSURE SWITCH ASSEMBLY
2 - VALVE BODY
3 - SCREEN

Fig. 242 Solenoid Retaining Screws

1 - SOLENOID/PRESSURE SWITCH ASSEMBLY
2 - RETAINING SCREWS

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AUTOMATIC TRANSMISSION - 42RLE

SOLENOID/PRESSURE SWITCH ASSY (Continued)

TORQUE CONVERTER

DESCRIPTION

The torque converter (Fig. 243) is a hydraulic

device that couples the engine crankshaft to the
transmission. The torque converter consists of an
outer shell with an internal turbine, a stator, an
overrunning clutch, an impeller and an electronically
applied converter clutch. The converter clutch pro-
vides reduced engine speed and greater fuel economy
when engaged. Clutch engagement also provides
reduced transmission fluid temperatures. The torque
converter hub drives the transmission oil (fluid)
pump.

The torque converter is a sealed, welded unit that

is not repairable and is serviced as an assembly.

CAUTION: The torque converter must be replaced if
a transmission failure resulted in large amounts of
metal or fiber contamination in the fluid.

Fig. 243 Torque Converter Assembly

1 - TURBINE
2 - IMPELLER
3 - HUB
4 - STATOR
5 - FRONT COVER
6 - CONVERTER CLUTCH DISC
7 - DRIVE PLATE

AUTOMATIC TRANSMISSION - 42RLE

21 - 141

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