Transmission fill DODGE RAM 1500 1998 2.G Manual Online

AUTOMATIC TRANSMISSION - 45RFE/545RFE
TABLE OF CONTENTS
page page
AUTOMATIC TRANSMISSION - 45RFE/545RFE
DESCRIPTION........................312
OPERATION..........................313
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - AUTOMATIC
TRANSMISSION.....................314
DIAGNOSIS AND TESTING -
PRELIMINARY.......................314
DIAGNOSIS AND TESTING - ROAD
TESTING...........................314
DIAGNOSIS AND TESTING - HYDRAULIC
PRESSURE TEST....................316
DIAGNOSIS AND TESTING - AIR CHECKING
TRANSMISSION CLUTCH OPERATION....317
DIAGNOSIS AND TESTING - CONVERTER
HOUSING FLUID LEAK................318
STANDARD PROCEDURE - ALUMINUM
THREAD REPAIR.....................318
REMOVAL............................318
DISASSEMBLY........................320
CLEANING...........................326
INSPECTION.........................326
ASSEMBLY...........................326
INSTALLATION........................333
SCHEMATICS AND DIAGRAMS
HYDRAULIC SCHEMATICS.............337
SPECIFICATIONS
TRANSMISSION.....................358
SPECIAL TOOLS
RFE TRANSMISSION.................359
4C RETAINER/BULKHEAD
DISASSEMBLY........................362
ASSEMBLY...........................363
ADAPTER HOUSING SEAL
REMOVAL............................364
INSTALLATION........................364
BRAKE TRANSMISSION SHIFT INTERLOCK
SYSTEM
DESCRIPTION........................364
OPERATION..........................364
DIAGNOSIS AND TESTING - BRAKE
TRANSMISSION SHIFT INTERLOCK......364
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK...................365
FLUID AND FILTER
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL.............366
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID.......................366DIAGNOSIS AND TESTING - FLUID
CONTAMINATION....................366
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK............................366
STANDARD PROCEDURE - FLUID AND
FILTER REPLACEMENT...............367
STANDARD PROCEDURE - TRANSMISSION
FILL...............................368
GEARSHIFT CABLE
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE.............................368
REMOVAL............................369
INSTALLATION........................370
ADJUSTMENTS
GEARSHIFT CABLE..................370
HOLDING CLUTCHES
DESCRIPTION........................371
OPERATION..........................372
INPUT CLUTCH ASSEMBLY
DESCRIPTION........................373
OPERATION..........................373
DISASSEMBLY........................374
ASSEMBLY...........................378
INPUT SPEED SENSOR
DESCRIPTION........................382
OPERATION..........................382
REMOVAL............................382
INSTALLATION........................382
LINE PRESSURE (LP) SENSOR
DESCRIPTION........................382
OPERATION..........................383
REMOVAL............................383
INSTALLATION........................383
LOW/REVERSE CLUTCH
DISASSEMBLY........................384
CLEANING...........................385
INSPECTION.........................385
ASSEMBLY...........................385
OIL PUMP
DESCRIPTION........................386
OPERATION..........................386
STANDARD PROCEDURE - OIL PUMP
VOLUME CHECK.....................387
DISASSEMBLY........................388
CLEANING...........................390
INSPECTION.........................390
ASSEMBLY...........................390
OIL PUMP FRONT SEAL
REMOVAL............................391
DRAUTOMATIC TRANSMISSION - 45RFE/545RFE 21 - 311

is applied. The clutch application can also be felt by
touching the appropriate element while applying air
pressure. As the air pressure is released, the clutch
should also release.
DIAGNOSIS AND TESTING - CONVERTER
HOUSING FLUID LEAK
When diagnosing converter housing fluid leaks,
two items must be established before repair.
(1) Verify that a leak condition actually exists.
(2) Determined the true source of the leak.
Some suspected converter housing fluid leaks may
not be leaks at all. They may only be the result of
residual fluid in the converter housing, or excess
fluid spilled during factory fill or fill after repair.
Converter housing leaks have several potential
sources. Through careful observation, a leak source
can be identified before removing the transmission
for repair. Torque converter seal leaks tend to move
along the drive hub and onto the rear of the con-
verter. Pump cover seal tend to run down the cover
and the inside surface of the bellhousing.
Some leaks, or suspected leaks, may be particu-
larly difficult to locate. If necessary, a Mopart
approved dye may be used to locate a leak.
TORQUE CONVERTER LEAK POINTS
Possible sources of converter leaks are:
(1) Leaks at the weld joint around the outside
diameter weld (Fig. 7).
(2) Leaks at the converter hub weld (Fig. 7).
STANDARD PROCEDURE - ALUMINUM
THREAD REPAIR
Damaged or worn threads in the aluminum trans-
mission case and valve body can be repaired by the
use of Heli-CoilsŸ, or equivalent. This repair con-
sists of drilling out the worn-out damaged threads.
Then tap the hole with a special Heli-CoilŸ tap, or
equivalent, and installing a Heli-CoilŸ insert, or
equivalent, into the hole. This brings the hole back to
its original thread size.
Heli-CoilŸ, or equivalent, tools and inserts are
readily available from most automotive parts suppli-
ers.
REMOVAL
(1) Disconnect the negative battery cable.
(2) Raise and support the vehicle
(3) Remove any necessary skid plates. (Refer to 13
- FRAMES & BUMPERS/FRAME/TRANSFER CASE
SKID PLATE - REMOVAL)
(4) Mark propeller shaft and axle companion
flanges for assembly alignment.
(5) Remove the rear propeller shaft
(6) Remove the front propeller shaft, if necessary.
(7) Remove the engine to transmission collar (Fig.
8).
(8) Remove the exhaust support bracket from the
rear of the transmission.
(9) Disconnect and lower or remove any necessary
exhaust components.
Fig. 7 Torque Converter Assembly
1 - TURBINE ASSEMBLY
2-STATOR
3 - CONVERTER HUB
4 - O-RING
5 - IMPELLER ASSEMBLY
6 - CONVERTER CLUTCH PISTON
7 - TURBINE HUB
Fig. 8 Transmission Collar
1 - ENGINE
2 - STRUCTURAL DUST COVER
3 - TRANSMISSION
21 - 318 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
AUTOMATIC TRANSMISSION - 45RFE/545RFE (Continued)

(22) Install torque converter-to-driveplate bolts.
Tighten bolts to 31 N´m (270 in. lbs.).
(23) Install starter motor and cooler line bracket.
(24) Connect cooler lines to transmission.
(25) Install transmission fill tube.
(26) Install exhaust components, if necessary.(27) Install the structural dust cover (Fig. 59)
(Refer to 9 - ENGINE/ENGINE BLOCK/STRUC-
TURAL COVER - INSTALLATION) onto the trans-
mission and the engine.
(28) Align and connect propeller shaft(s).
(29) Adjust gearshift cable if necessary.
(30) Install any skid plates removed previously.
(Refer to 13 - FRAMES & BUMPERS/FRAME/
TRANSFER CASE SKID PLATE - INSTALLATION)
(31) Lower vehicle.
(32) Fill transmission with MopartATF +4, Auto-
matic Transmission Fluid.
Fig. 58 Connect Line Pressure Sensor
1 - TRANSMISSION
2 - LINE PRESSURE SENSOR
Fig. 59 Transmission Collar
1 - ENGINE
2 - STRUCTURAL DUST COVER
3 - TRANSMISSION
21 - 336 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
AUTOMATIC TRANSMISSION - 45RFE/545RFE (Continued)

FLUID AND FILTER
DIAGNOSIS AND TESTING
DIAGNOSIS AND TESTING - EFFECTS OF
INCORRECT FLUID LEVEL
A low fluid level allows the pump to take in air
along with the fluid. Air in the fluid will cause fluid
pressures to be low and develop slower than normal.
If the transmission is overfilled, the gears churn the
fluid into foam. This aerates the fluid and causing
the same conditions occurring with a low level. In
either case, air bubbles cause fluid overheating, oxi-
dation and varnish buildup which interferes with
valve and clutch operation. Foaming also causes fluid
expansion which can result in fluid overflow from the
transmission vent or fill tube. Fluid overflow can eas-
ily be mistaken for a leak if inspection is not careful.
DIAGNOSIS AND TESTING - CAUSES OF
BURNT FLUID
Burnt, discolored fluid is a result of overheating
which has three primary causes.
(1) Internal clutch slippage, usually caused by low
line pressure, inadequate clutch apply pressure, or
clutch seal failure.
(2) A result of restricted fluid flow through the
main and/or auxiliary cooler. This condition is usu-
ally the result of a faulty or improperly installed
drainback valve, a damaged main cooler, or severe
restrictions in the coolers and lines caused by debris
or kinked lines.
(3) Heavy duty operation with a vehicle not prop-
erly equipped for this type of operation. Trailer tow-
ing or similar high load operation will overheat the
transmission fluid if the vehicle is improperly
equipped. Such vehicles should have an auxiliary
transmission fluid cooler, a heavy duty cooling sys-
tem, and the engine/axle ratio combination needed to
handle heavy loads.
DIAGNOSIS AND TESTING - FLUID
CONTAMINATION
Transmission fluid contamination is generally a
result of:
²adding incorrect fluid
²failure to clean dipstick and fill tube when
checking level
²engine coolant entering the fluid
²internal failure that generates debris
²overheat that generates sludge (fluid break-
down)
²failure to replace contaminated converter after
repairThe use of non-recommended fluids can result in
transmission failure. The usual results are erratic
shifts, slippage, abnormal wear and eventual failure
due to fluid breakdown and sludge formation. Avoid
this condition by using recommended fluids only.
The dipstick cap and fill tube should be wiped
clean before checking fluid level. Dirt, grease and
other foreign material on the cap and tube could fall
into the tube if not removed beforehand. Take the
time to wipe the cap and tube clean before withdraw-
ing the dipstick.
Engine coolant in the transmission fluid is gener-
ally caused by a cooler malfunction. The only remedy
is to replace the radiator as the cooler in the radiator
is not a serviceable part. If coolant has circulated
through the transmission, an overhaul is necessary.
The torque converter should also be replaced when-
ever a failure generates sludge and debris. This is
necessary because normal converter flushing proce-
dures will not remove all contaminants.
STANDARD PROCEDURE
STANDARD PROCEDURE - FLUID LEVEL
CHECK
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with
the fluid. As in any hydraulic system, air bubbles
make the fluid spongy, therefore, pressures will be
low and build up slowly.
Improper filling can also raise the fluid level too
high. When the transmssion has too much fluid, the
geartrain churns up foam and cause the same condi-
tions which occur with a low fluid level.
In either case, air bubbles can cause overheating
and/or fluid oxidation, and varnishing. This can
interfere with normal valve, clutch, and accumulator
operation. Foaming can also result in fluid escaping
from the transmission vent where it may be mis-
taken for a leak.
After the fluid has been checked, seat the dipstick
fully to seal out water and dirt.
The transmission has a dipstick to check oil level.
It is located on the right side of the engine. Be sure
to wipe all dirt from dipstick handle before removing.
The torque converter fills in both the P (PARK)
and N (NEUTRAL) positions. Place the selector lever
in P (PARK) to be sure that the fluid level check is
accurate.The engine should be running at idle
speed for at least one minute, with the vehicle
on level ground.At normal operating temperature
(approximately 82 C. or 180 F.), the fluid level is cor-
rect if it is in the HOT region (cross-hatched area) on
the oil level indicator. The fluid level will be approx-
21 - 366 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR

imately at the upper COLD hole of the dipstick at
70É F fluid temperature.
NOTE: Engine and Transmission should be at nor-
mal operating temperature before performing this
procedure.
(1) Start engine and apply parking brake.
(2) Shift the transmission into DRIVE for approxi-
mately 2 seconds.
(3) Shift the transmission into REVERSE for
approximately 2 seconds.
(4) Shift the transmission into PARK.
(5) Hook up DRBtscan tool and select transmis-
sion.
(6) Select sensors.
(7) Read the transmission temperature value.
(8) Compare the fluid temperature value with the
chart. (Fig. 66)
(9) Adjust transmission fluid level shown on the
dipstick according to the chart.
NOTE: After adding any fluid to the transmission,
wait a minimum of 2 minutes for the oil to fully
drain from the fill tube into the transmission before
rechecking the fluid level.
(10) Check transmission for leaks.STANDARD PROCEDURE - FLUID AND FILTER
REPLACEMENT
For proper service intervals (Refer to LUBRICA-
TION & MAINTENANCE/MAINTENANCE SCHED-
ULES - DESCRIPTION).
REMOVAL
(1) Hoist and support vehicle on safety stands.
(2) Place a large diameter shallow drain pan
beneath the transmission pan.
(3) Remove bolts holding front and sides of pan to
transmission.
(4) Loosen bolts holding rear of pan to transmis-
sion.
(5) Slowly separate front of pan away from trans-
mission allowing the fluid to drain into drain pan.
(6) Hold up pan and remove remaining bolts hold-
ing pan to transmission.
(7) While holding pan level, lower pan away from
transmission.
(8) Pour remaining fluid in pan into drain pan.
(9) Remove screw holding filter to valve body (Fig.
67).
(10) Separate filter from valve body and oil pump
and pour fluid in filter into drain pan.
Fig. 66 Transmission Fluid Temperature Chart
DRAUTOMATIC TRANSMISSION - 45RFE/545RFE 21 - 367
FLUID AND FILTER (Continued)

(11) Remove and discard the oil filter seal from the
bottom of the oil pump.
(12) If replacing the cooler return filter, use Oil
Filter Wrench 8321 to remove the filter from the
transmission.
(13) Dispose of used trans fluid and filter(s) prop-
erly.
INSPECTION
Inspect bottom of pan and magnet for excessive
amounts of metal. A light coating of clutch material
on the bottom of the pan does not indicate a problem
unless accompanied by a slipping condition or shift
lag. If fluid and pan are contaminated with excessive
amounts of debris, refer to the diagnosis section of
this group.
CLEANING
(1) Using a suitable solvent, clean pan and mag-
net.
(2) Using a suitable gasket scraper, clean original
sealing material from surface of transmission case
and the transmission pan.
INSTALLATION
CAUTION: The primary oil filter seal MUST be fully
installed flush against the oil pump body. DO NOT
install the seal onto the filter neck and attempt to
install the filter and seal as an assembly. Damage to
the transmission will result.
(1) Install a new primary oil filter seal in the oil
pump inlet bore. Seat the seal in the bore with the
butt end of a hammer, or other suitable tool.(2) Place replacement filter in position on valve
body and into the oil pump.
(3) Install screw to hold filter to valve body (Fig.
67). Tighten screw to 4.5 N´m (40 in. lbs.) torque.
(4) Install new cooler return filter onto the trans-
mission, if necessary. Torque the filter to 14.12 N´m
(125 in.lbs.).
(5) Place bead of MopartRTV sealant onto the
transmission case sealing surface.
(6) Place pan in position on transmission.
(7) Install bolts to hold pan to transmission.
Tighten bolts to 11.8 N´m (105 in. lbs.) torque.
(8) Lower vehicle and fill transmission with
MopartATF +4.
STANDARD PROCEDURE - TRANSMISSION
FILL
To avoid overfilling transmission after a fluid
change or overhaul, perform the following procedure:
(1) Remove dipstick and insert clean funnel in
transmission fill tube.
(2) Add following initial quantity of MopartAT F
+4 to transmission:
(a) If only fluid and filter were changed, add10
pints (5 quarts)of ATF +4 to transmission.
(b) If transmission was completely overhauled
and the torque converter was replaced or drained,
add24 pints (12 quarts)of ATF +4 to transmis-
sion.
(3) Check the transmission fluid (Refer to 21 -
TRANSMISSION/AUTOMATIC - RFE/FLUID -
STANDARD PROCEDURE) and adjust as required.
GEARSHIFT CABLE
DIAGNOSIS AND TESTING - GEARSHIFT
CABLE
(1) Engine starts must be possible with shift lever
in PARK or NEUTRAL positions only. Engine starts
must not be possible in any other gear position.
(2) With the shift lever in the:
(a) PARK position - Apply upward force on the
shift arm and remove pressure. Engine starts must
be possible.
(b) PARK position - Apply downward force on
the shift arm and remove pressure. Engine starts
must be possible.
(c) NEUTRAL position - Normal position. Engine
starts must be possible.
(d) NEUTRAL position - Engine running and
brakes applied, apply upward force on the shift
arm. Transmission shall not be able to shift from
neutral to reverse.
Fig. 67 Transmission Filters - 4X4 Shown
1 - PRIMARY OIL FILTER
2 - COOLER RETURN FILTER
3 - COOLER RETURN FILTER BYPASS VALVE
4 - VALVE BODY
21 - 368 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
FLUID AND FILTER (Continued)

CONVERTER CLUTCH REGULATOR VALVE
The converter clutch regulator valve is used to con-
trol the hydraulic pressure supplied to the back (ON)
side of the torque converter clutch.
TORQUE CONVERTER LIMIT VALVE
The torque converter limit valve serves to limit the
available line pressure to the torque converter clutch.
STANDARD PROCEDURE - OIL PUMP VOLUME
CHECK
Measuring the oil pump output volume will deter-
mine if sufficient oil flow to the transmission oil
cooler exists, and whether or not an internal trans-
mission failure is present.Verify that the transmission fluid is at the proper
level. Refer to the Fluid Level Check procedure in
this section. If necessary, fill the transmission to the
proper level with MopartATF +4, Automatic Trans-
mission Fluid.
(1) Disconnect theTo coolerline at the cooler
inlet and place a collecting container under the dis-
connected line.
CAUTION: With the fluid set at the proper level,
fluid collection should not exceed (1) quart or inter-
nal damage to the transmission may occur.
(2) Run the engineat 1800 rpm, with the shift
selector in neutral. Verify that the transmission fluid
temperature is below 104.5É C (220É F) for this test.
Fig. 99 Oil Pump Reaction Shaft
1 - PUMP HOUSING 4 - SEAL RING (5)
2 - SEAL 5 - REACTION SHAFT SUPPORT
3 - OIL FILTER SEAL 6 - PUMP VALVE BODY
DRAUTOMATIC TRANSMISSION - 45RFE/545RFE 21 - 387
OIL PUMP (Continued)

(3) If one quart of transmission fluid is collected in
the container in 30 seconds or less, oil pump flow vol-
ume is within acceptable limits. If fluid flow is inter-
mittent, or it takes more than 30 seconds to collect
one quart of fluid, refer to the Hydraulic Pressure
tests in this section for further diagnosis.
(4) Re-connect theTo coolerline to the transmis-
sion cooler inlet.
(5) Refill the transmission to proper level.
DISASSEMBLY
(1) Remove the bolts holding the reaction shaft
support to the oil pump (Fig. 100).
(2) Remove the reaction shaft support from the oil
pump (Fig. 100).(3) Remove all bolts holding the oil pump halves
together (Fig. 100).
(4) Using suitable prying tools, separate the oil
pump sections by inserting the tools in the supplied
areas and prying the halves apart.
NOTE: The oil pump halves are aligned to each
other through the use of two dowels. Be sure to pry
upward evenly to prevent damage to the oil pump
components.
(5) Remove the screws holding the separator plate
onto the oil pump body (Fig. 101).
(6) Remove the separator plate from the oil pump
body (Fig. 101).
Fig. 100 Oil Pump Assembly
1 - PUMP HOUSING 4 - SEAL RING (5)
2 - SEAL 5 - REACTION SHAFT SUPPORT
3 - OIL FILTER SEAL 6 - PUMP VALVE BODY
21 - 388 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
OIL PUMP (Continued)

PRESSURE ON A CONFINED FLUID
Pressure is exerted on a confined fluid (Fig. 111) by
applying a force to some given area in contact with
the fluid. A good example of this is a cylinder filled
with fluid and equipped with a piston that is closely
fitted to the cylinder wall. If a force is applied to the
piston, pressure will be developed in the fluid. Of
course, no pressure will be created if the fluid is not
confined. It will simply ªleakº past the piston. There
must be a resistance to flow in order to create pres-
sure. Piston sealing is extremely important in
hydraulic operation. Several kinds of seals are used
to accomplish this within a transmission. These
include but are not limited to O-rings, D-rings, lip
seals, sealing rings, or extremely close tolerances
between the piston and the cylinder wall. The force
exerted is downward (gravity), however, the principle
remains the same no matter which direction is taken.
The pressure created in the fluid is equal to the force
applied, divided by the piston area. If the force is 100
lbs., and the piston area is 10 sq. in., then the pres-
sure created equals 10 PSI. Another interpretation of
Pascal's Law is that regardless of container shape or
size, the pressure will be maintained throughout, as
long as the fluid is confined. In other words, the
pressure in the fluid is the same everywhere within
the container.
FORCE MULTIPLICATION
Using the 10 PSI example used in the illustration
(Fig. 112), a force of 1000 lbs. can be moved with a
force of only 100 lbs. The secret of force multiplica-
tion in hydraulic systems is the total fluid contact
area employed. The illustration, (Fig. 112), shows an
area that is ten times larger than the original area.
The pressure created with the smaller 100 lb. input
is 10 PSI. The concept ªpressure is the same every-
whereº means that the pressure underneath the
larger piston is also 10 PSI. Pressure is equal to the
force applied divided by the contact area. Therefore,
by means of simple algebra, the output force may be
found. This concept is extremely important, as it is
also used in the design and operation of all shift
valves and limiting valves in the valve body, as well
as the pistons, of the transmission, which activate
the clutches and bands. It is nothing more than
using a difference of area to create a difference in
pressure to move an object.
Fig. 111 Pressure on a Confined Fluid
Fig. 112 Force Multiplication
21 - 394 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR
PISTONS (Continued)

SHIFT MECHANISM
DESCRIPTION
The gear shift mechanism provides six shift posi-
tions which are:
²Park (P)
²Reverse (R)
²Neutral (N)
²Drive (D)
²Manual second (2)
²Manual low (1)
OPERATION
MANUAL LOW (1) range provides first gear only.
Overrun braking is also provided in this range.
MANUAL SECOND (2) range provides first and sec-
ond gear only.
DRIVE range provides FIRST, SECOND, THIRD,
OVERDRIVE FOURTH, and OVERDRIVE FIFTH (if
applicable) gear ranges. The shift into OVERDRIVE
FOURTH and FIFTH (if applicable) gear ranges
occurs only after the transmission has completed the
shift into D THIRD gear range. No further movement
of the shift mechanism is required to complete the
3-4 or 4-5 (if applicable) shifts.
The FOURTH and FIFTH (if applicable) gear
upshifts occur automatically when the overdrive
selector switch is in the ON position. No upshift to
FOURTH or FIFTH (if applicable) gears will occur if
any of the following are true:
²The transmission fluid temperature is below 10É
C (50É F) or above 121É C (250É F).
²The shift to THIRD is not yet complete.
²Vehicle speed is too low for the 3-4 or 4-5 (if
applicable) shifts to occur.
Upshifts into FOURTH or FIFTH (if applicable)
will be delayed when the transmission fluid temper-
ature is below 4.5É C (40É F) or above 115.5É C (240É
F).
SOLENOID SWITCH VALVE
DESCRIPTION
The Solenoid Switch Valve (SSV) is located in the
valve body and controls the direction of the transmis-
sion fluid when the L/R-TCC solenoid is energized.
OPERATION
The Solenoid Switch Valve controls line pressure
from the LR-TCC solenoid. In 1st gear, the SSV will
be in the downshifted position, thus directing fluid to
the L/R clutch circuit. In 2nd, 3rd, 4th, and 5th (if
applicable) gears, the solenoid switch valve will be in
the upshifted position and directs the fluid into the
torque converter clutch (TCC) circuit.When shifting into 1st gear, a special hydraulic
sequence is performed to ensure SSV movement into
the downshifted position. The L/R pressure switch is
monitored to confirm SSV movement. If the move-
ment is not confirmed (the L/R pressure switch does
not close), 2nd gear is substituted for 1st. A DTC will
be set after three unsuccessful attempts are made to
get into 1st gear in one given key start.
SOLENOIDS
DESCRIPTION
The typical electrical solenoid used in automotive
applications is a linear actuator. It is a device that
produces motion in a straight line. This straight line
motion can be either forward or backward in direc-
tion, and short or long distance.
A solenoid is an electromechanical device that uses
a magnetic force to perform work. It consists of a coil
of wire, wrapped around a magnetic core made from
steel or iron, and a spring loaded, movable plunger,
which performs the work, or straight line motion.
The solenoids used in transmission applications
are attached to valves which can be classified asnor-
mally openornormally closed. Thenormally
opensolenoid valve is defined as a valve which
allows hydraulic flow when no current or voltage is
applied to the solenoid. Thenormally closedsole-
noid valve is defined as a valve which does not allow
hydraulic flow when no current or voltage is applied
to the solenoid. These valves perform hydraulic con-
trol functions for the transmission and must there-
fore be durable and tolerant of dirt particles. For
these reasons, the valves have hardened steel pop-
pets and ball valves. The solenoids operate the valves
directly, which means that the solenoids must have
very high outputs to close the valves against the siz-
able flow areas and line pressures found in current
transmissions. Fast response time is also necessary
to ensure accurate control of the transmission.
The strength of the magnetic field is the primary
force that determines the speed of operation in a par-
ticular solenoid design. A stronger magnetic field will
cause the plunger to move at a greater speed than a
weaker one. There are basically two ways to increase
the force of the magnetic field:
1. Increase the amount of current applied to the
coil or
2. Increase the number of turns of wire in the coil.
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.
21 - 398 AUTOMATIC TRANSMISSION - 45RFE/545RFEDR