Shifting DODGE RAM 1500 1998 2.G User Guide

IDENTIFICATION
The transmission has two identification tags
attached to the driver side upper clutch housing (Fig.
2). One tag provides the transmission part number.
The second tag provides sequencing and build date
information. The information on the tags are essen-
tial to correct parts ordering.
OPERATION
The driver selects a particular gear by moving the
shift lever to the desired gear position. As the shift
lever moves the selected shift rail, the shift fork
attached to that rail begins to move. The fork is posi-
tioned in a groove in the outer circumference of the
synchronizer sleeve. As the shift fork moves the syn-
chronizer sleeve, the synchronizer begins to speed-up
or slow down the selected gear (depending on
whether we are up-shifting or down-shifting). The
synchronizer does this by having the synchronizer
hub splined to the mainshaft or the countershaft in
some cases, and moving the blocker ring into contact
with the gear's friction cone. As the blocker ring and
friction cone come together, the gear speed is brought
up or down to the speed of the synchronizer. As the
two speeds match, the splines on the inside of the
synchronizer sleeve become aligned with the teeth on
the blocker ring and friction cone and eventually will
slide over the teeth, locking the gear to the main-
shaft or countershaft through the synchronizer.
DIAGNOSIS AND TESTING
LOW LUBRICANT LEVEL
A low transmission lubricant level is generally the
result of a leak, inadequate lubricant fill or an incor-
rect lubricant level check. A correct lubricant level
check can only be made when the vehicle is level.
Also allow the lubricant to settle for a minute or sobefore checking. These recommendations will ensure
an accurate check and avoid an underfill or overfill
condition. Always check the lubricant level after any
addition of fluid to avoid an incorrect lubricant level
condition.
Leaks can occur at the mating surfaces of the gear
case, adaptor or extension housing, or from the front/
rear seals. A suspected leak could also be the result
of an overfill condition. Leaks at the rear of the
extension or adapter housing will be from the hous-
ing oil seals. Leaks at component mating surfaces
will probably be the result of inadequate sealer, gaps
in the sealer, incorrect bolt tightening or use of a
non-recommended sealer. A leak at the front of the
transmission will be from either the front bearing
retainer or retainer seal. Lubricant may be seen drip-
ping from the clutch housing after extended opera-
tion. If the leak is severe, it may also contaminate
the clutch disc causing the disc to slip, grab and or
chatter.
HARD SHIFTING
Hard shifting is usually caused by a low lubricant
level, improper or contaminated lubricants. The con-
sequence of using non-recommended lubricants is
noise, excessive wear, internal bind and hard shift-
ing. Substantial lubricant leaks can result in gear,
shift rail, synchro, and bearing damage. If a leak
goes undetected for an extended period, the first indi-
cations of component damage are usually hard shift-
ing and noise.
Component damage, incorrect clutch adjustment or
damaged clutch pressure plate or disc are additional
probable causes of increased shift effort. Incorrect
adjustment or a worn/damaged pressure plate or disc
can cause incorrect release. If clutch problem is
advanced, gear clash during shifts can result. Worn
or damaged synchro rings can cause gear clash when
shifting into any forward gear. In some new or
rebuilt transmissions, new synchro rings may tend to
stick slightly causing hard or noisy shifts. In most
cases this condition will decline as the rings wear-in.
TRANSMISSION NOISE
Most manual transmissions make some noise dur-
ing normal operation. Rotating gears generate a mild
whine that is audible, but generally only at extreme
speeds. Severe highly audible transmission noise is
generally the initial indicator of a lubricant problem.
Insufficient, improper or contaminated lubricant
will promote rapid wear of gears, synchros, shift
rails, forks and bearings. The overheating caused by
a lubricant problem, can also lead to gear breakage.
REMOVAL
(1) Shift transmission into Neutral.
Fig. 2 IDENTIFICATION TAG LOCATION
1 - IDENTIFICATION TAGS
21 - 90 MANUAL TRANSMISSION - NV5600DR
MANUAL TRANSMISSION - NV5600 (Continued)

SECOND GEAR POWERFLOW
In DRIVE-SECOND (Fig. 7), the same elements
are applied as in MANUAL-SECOND. Therefore, the
power flow will be the same, and both gears will be
discussed as one in the same. In DRIVE-SECOND,
the transmission has proceeded from first gear to its
shift point, and is shifting from first gear to second.
The second gear shift is obtained by keeping the rear
clutch applied and applying the front (kickdown)
band. The front band holds the front clutch retainer
that is locked to the sun gear driving shell. With the
rear clutch still applied, the input is still on the front
annulus gear turning it clockwise at engine speed.Now that the front band is holding the sun gear sta-
tionary, the annulus rotation causes the front planets
to rotate in a clockwise direction. The front carrier is
then also made to rotate in a clockwise direction but
at a reduced speed. This will transmit the torque to
the output shaft, which is directly connected to the
front planet carrier. The rear planetary annulus gear
will also be turning because it is directly splined to
the output shaft. All power flow has occurred in the
front planetary gear set during the drive-second
stage of operation, and now the over-running clutch,
in the rear of the transmission, is disengaged and
freewheeling on its hub.
Fig. 7 Second Gear Powerflow
1 - KICKDOWN BAND APPLIED 6 - INPUT SHAFT
2 - OUTPUT SHAFT 7 - REAR CLUTCH APPLIED
3 - REAR CLUTCH ENGAGED 8 - KICKDOWN BAND APPLIED
4 - OUTPUT SHAFT 9 - INPUT SHAFT
5 - OVER-RUNNING CLUTCH FREE-WHEELING
21 - 138 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

CONDITION POSSIBLE CAUSES CORRECTION
DELAYED ENGAGEMENT
(FROM NEUTRAL TO
DRIVE OR REVERSE)1. Fluid Level Low. 1. Correct level and check for leaks.
2. Filter Clogged. 2. Change filter.
3. Gearshift Linkage Mis-adjusted. 3. Adjust linkage and repair linkage if worn
or damaged.
4. Torque Converter Drain Back (Oil
drains from torque converter into
transmission sump).4. If vehicle moves normally after 5
seconds after shifting into gear, no repair is
necessary. If longer, inspect pump bushing
for wear. Replace pump house.
5. Rear Band Mis-adjusted. 5. Adjust band.
6. Valve Body Filter Plugged. 6. Replace fluid and filter. If oil pan and old
fluid were full of clutch disc material and/or
metal particles, overhaul will be necessary.
7. Oil Pump Gears Worn/Damaged. 7. Remove transmission and replace oil
pump.
8. Governor Circuit and Solenoid
Valve Electrical Fault.8. Test with DRBTscan tool and repair as
required.
9. Hydraulic Pressure Incorrect. 9. Perform pressure test, remove
transmission and repair as needed.
10. Reaction Shaft Seal Rings
Worn/Broken.10. Remove transmission, remove oil pump
and replace seal rings.
11. Rear Clutch/Input Shaft, Rear
Clutch Seal Rings Damaged.11. Remove and disassemble transmission
and repair as necessary.
12. Regulator Valve Stuck. 12. Clean.
13. Cooler Plugged. 13. Transfer case failure can plug cooler.
NO DRIVE RANGE
(REVERSE OK)1. Fluid Level Low. 1. Add fluid and check for leaks if drive is
restored.
2. Gearshift Linkage/Cable
Loose/Misadjusted.2. Repair or replace linkage components.
3. Rear Clutch Burnt. 3. Remove and disassemble transmission
and rear clutch and seals. Repair/replace
worn or damaged parts as needed.
4. Valve Body Malfunction. 4. Remove and disassemble valve body.
Replace assembly if any valves or bores
are damaged.
5. Transmission Overrunning Clutch
Broken.5. Remove and disassemble transmission.
Replace overrunning clutch.
6. Input Shaft Seal Rings Worn/
Damaged.6. Remove and disassemble transmission.
Replace seal rings and any other worn or
damaged parts.
7. Front Planetary Failed Broken. 7. Remove and repair.
DRAUTOMATIC TRANSMISSION - 48RE 21 - 147
AUTOMATIC TRANSMISSION - 48RE (Continued)

PRESSURE TEST
Overdrive clutch Fourth gear only Pressure should be 524-565 kPa (76-82 psi) with
closed throttle and increase to 965 kPa (140 psi) at 1/2
to 3/4 throttle.
Line pressure (at
accumulator)Closed throttle 372-414 kPa (54-60 psi).
Front servo Third or Fourth gear only No more than 21 kPa (3 psi) lower than line pressure.
Rear servo 1 range No more than 21 kPa (3 psi) lower than line pressure.
R range 1103 kPa (160 psi) at idle, builds to 1862 kPa (270 psi)
at 1600 rpm.
Governor D range closed throttle Pressure should respond smoothly to changes in mph
and return to 0-7 kPa (0-1.5 psi) when stopped with
transmission in D, 1, 2. Pressure above 7 kPa (1.5 psi)
at stand still will prevent transmission from
downshifting.
TORQUE SPECIFICATIONS
DESCRIPTION N´m Ft. Lbs. In. Lbs.
Fitting, cooler line at trans 18 13 -
Bolt, torque convertor 47 35 -
Bolt, clevis bracket to crossmember 47 35 -
Bolt, clevis bracket to rear support 68 50 -
Bolt, driveplate to crankshaft 75 55 -
Plug, front band reaction 17 13 -
Locknut, front band adj. 34 25 -
Bolt, fluid pan 13.6 - 120
Screws, fluid filter 4 - 35
Bolt, oil pump 20 15 -
Bolt, overrunning clutch cam 17 13 -
Bolt, O/D to trans. 34 25 -
Bolt, O/D piston retainer 17 13 -
Plug, pressure test port 14 10 -
Bolt, reaction shaft support 20 15 -
Locknut, rear band 41 30 -
Bolt, valve body to case 12 - 100
Sensor, trans speed 27 20 -
Screw, solenoid wiring connector 4 - 35
Screw, solenoid to transfer plate 4 - 35
Bracket, transmission range sensor mounting 34 25 -
Screw, transmision range sensor to mounting
bracket5-45
21 - 190 AUTOMATIC TRANSMISSION - 48REDR
AUTOMATIC TRANSMISSION - 48RE (Continued)

BRAKE TRANSMISSION SHIFT
INTERLOCK SYSTEM
DESCRIPTION
The Brake Transmission Shifter Interlock (BTSI)
(Fig. 74), is a solenoid operated system. It consists of
a solenoid permanently mounted on the gearshift
cable.
OPERATION
The system locks the shifter into the PARK posi-
tion. The interlock system is engaged whenever the
ignition switch is in the LOCK or ACCESSORY posi-
tion. An additional electrically activated feature will
prevent shifting out of the PARK position unless the
brake pedal is depressed approximately one-half an
inch. A magnetic holding device in line with the park
lock cable is energized when the ignition is in the
RUN position. When the key is in the RUN position
and the brake pedal is depressed, the shifter is
unlocked and will move into any position. The inter-
lock system also prevents the ignition switch from
being turned to the LOCK or ACCESSORY position,
unless the shifter is fully locked into the PARK posi-
tion.
DIAGNOSIS AND TESTING - BRAKE
TRANSMISSION SHIFT INTERLOCK
(1) Verify that the key can only be removed in the
PARK position
(2) When the shift lever is in PARK And the shift
handle pushbutton is in the ªOUTº position, the igni-
tion key cylinder should rotate freely from OFF toLOCK. When the shifter is in any other gear or neu-
tral position, the ignition key cylinder should not
rotate to the LOCK position.
(3) Shifting out of PARK should not be possible
when the ignition key cylinder is in the OFF posi-
tion.
(4) Shifting out of PARK should not be possible
while applying normal pushbutton force and ignition
key cylinder is in the RUN or START positions
unless the foot brake pedal is depressed approxi-
mately 1/2 inch (12mm).
(5) Shifting out of PARK should not be possible
when the ignition key cylinder is in the ACCESSORY
or LOCK positions.
(6) Shifting between any gears, NEUTRAL or into
PARK may be done without depressing foot brake
pedal with ignition switch in RUN or START posi-
tions.
ADJUSTMENTS - BRAKE TRANSMISSION
SHIFT INTERLOCK
Correct cable adjustment is important to proper
interlock operation. The gearshift cable must be cor-
rectly adjusted in order to shift out of PARK.
ADJUSTMENT PROCEDURE
(1) Remove the steering column trim as necessary
for access to the brake transmission shift interlock.
(2) Shift the transmission into the PARK position.
(3) Pull upward on both the BTSI lock tab and the
gearshift cable lock tab (Fig. 75).
(4) Verify that the shift lever is in the PARK posi-
tion.
(5) Verify positive engagement of the transmission
park lock by attempting to rotate the propeller shaft.
The shaft will not rotate when the park lock is
engaged.
(6) Turn ignition switch to LOCK position.Be
sure ignition key cylinder is in the LOCK posi-
tion. Cable will not adjust correctly in any
other position.
(7) Ensure that the cable is free to self-adjust by
pushing cable rearward and releasing.
(8) Push the gearshift cable lock tab down until it
snaps in place.
(9) Locate the BTSI alignment hole in the bottom
of the BTSI mechanism between the BTSI lock tab
and the BTSI connector.
(10) Move the BTSI assembly up or down on the
gearshift cable until an appropriate size drill bit can
be inserted into the alignment hole and through the
assembly.
(11) Push the BTSI lock tab down until it snaps
into place and remove the drill bit.
(12) Install any steering column trim previously
removed.
Fig. 74 Brake Transmission Interlock Mechanism
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
21 - 196 AUTOMATIC TRANSMISSION - 48REDR

BTSI FUNCTION CHECK
(1) Verify removal of ignition key allowed in PARK
position only.
(2) When the shift lever is in PARK, the ignition
key cylinder should rotate freely from off to lock.
When the shifter is in any other position, the ignition
key should not rotate from off to lock.
(3) Shifting out of PARK should be possible when
the ignition key cylinder is in the off position.
(4) Shifting out of PARK should not be possible
while applying normal force, and ignition key cylin-
der is in the run or start positions, unless the foot
brake pedal is depressed approximately 1/2 inch
(12mm).
(5) Shifting out of PARK should not be possible
when the ignition key cylinder is in the accessory or
lock position.
(6) Shifting between any gear and NEUTRAL, or
PARK, may be done without depressing foot brake
with ignition switch in run or start positions.
(7) Engine starts must be possible with shifter
lever in PARK or NEUTRAL positions only. Engine
starts must not be possible in any position other than
PARK or NEUTRAL.
(8) With shifter lever in the:
²PARK position - Apply upward force on the shift
arm and remove pressure. Engine starts must be
possible.²PARK position - Apply downward force on the
shift arm and remove pressure. Engine starts must
be possible.
²NEUTRAL position - Normal position. Engine
starts must be possible.
²NEUTRAL position - Engine running and brakes
applied, apply upward force on the shift arm. Trans-
mission shall not be able to shift from neutral to
reverse.
ELECTRONIC GOVERNOR
DESCRIPTION
Governor pressure is controlled electronically. Com-
ponents used for governor pressure control include:
²Governor body
²Valve body transfer plate
²Governor pressure solenoid valve
²Governor pressure sensor
²Fluid temperature thermistor
²Throttle position sensor (TPS)
²Transmission speed sensor
²Powertrain control module (PCM)
GOVERNOR PRESSURE SOLENOID VALVE
The solenoid valve is a duty-cycle solenoid which
regulates the governor pressure needed for upshifts
and downshifts. It is an electro-hydraulic device
located in the governor body on the valve body trans-
fer plate (Fig. 76).
Fig. 75 Brake Transmission Interlock Mechanism
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
Fig. 76 Governor Pressure Solenoid Valve
1 - SOLENOID FILTER
2 - GOVERNOR PRESSURE SOLENOID
DRAUTOMATIC TRANSMISSION - 48RE 21 - 197
BRAKE TRANSMISSION SHIFT INTERLOCK SYSTEM (Continued)

GOVERNOR PRESSURE SENSOR
The governor pressure sensor measures output
pressure of the governor pressure solenoid valve (Fig.
77).
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate is designed to supply transmis-
sion line pressure to the governor pressure solenoid
valve and to return governor pressure.
The governor pressure solenoid valve is mounted in
the governor body. The body is bolted to the lower
side of the transfer plate (Fig. 77).
GOVERNOR PRESSURE CURVES
There are four governor pressure curves pro-
grammed into the transmission control module. The
different curves allow the control module to adjust
governor pressure for varying conditions. One curve
is used for operation when fluid temperature is at, or
below, ±1ÉC (30ÉF). A second curve is used when fluid
temperature is at, or above, 10ÉC (50ÉF) during nor-
mal city or highway driving. A third curve is used
during wide-open throttle operation. The fourth curve
is used when driving with the transfer case in low
range.
OPERATION
Compensation is required for performance varia-
tions of two of the input devices. Though the slope of
the transfer functions is tightly controlled, offset may
vary due to various environmental factors or manu-
facturing tolerances.
The pressure transducer is affected by barometric
pressure as well as temperature. Calibration of the
zero pressure offset is required to compensate for
shifting output due to these factors.
Normal calibration will be performed when sump
temperature is above 50 degrees F, or in the absenceof sump temperature data, after the first 10 minutes
of vehicle operation. Calibration of the pressure
transducer offset occurs each time the output shaft
speed falls below 200 RPM. Calibration shall be
repeated each 3 seconds the output shaft speed is
below 200 RPM. A 0.5 second pulse of 95% duty cycle
is applied to the governor pressure solenoid valve
and the transducer output is read during this pulse.
Averaging of the transducer signal is necessary to
reject electrical noise.
Under cold conditions (below 50 degrees F sump),
the governor pressure solenoid valve response may
be too slow to guarantee 0 psi during the 0.5 second
calibration pulse. Calibration pulses are continued
during this period, however the transducer output
valves are discarded. Transducer offset must be read
at key-on, under conditions which promote a stable
reading. This value is retained and becomes the off-
set during the9cold9period of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to
normal transmission line pressure. The outlet side of
the valve leads to the valve body governor circuit.
The solenoid valve regulates line pressure to pro-
duce governor pressure. The average current sup-
plied to the solenoid controls governor pressure. One
amp current produces zero kPa/psi governor pres-
sure. Zero amps sets the maximum governor pres-
sure.
The powertrain control module (PCM) turns on the
trans control relay which supplies electrical power to
the solenoid valve. Operating voltage is 12 volts
(DC). The PCM controls the ground side of the sole-
noid using the governor pressure solenoid control cir-
cuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary
feedback to the PCM. This feedback is needed to ade-
quately control governor pressure.
GOVERNOR BODY AND TRANSFER PLATE
The transfer plate channels line pressure to the
solenoid valve through the governor body. It also
channels governor pressure from the solenoid valve
to the governor circuit. It is the solenoid valve that
develops the necessary governor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conven-
tional governor can delay shifts, resulting in higher
than normal shift speeds and harsh shifts. The elec-
tronically controlled low temperature governor pres-
Fig. 77 Governor Pressure Sensor
1 - GOVERNOR BODY
2 - GOVERNOR PRESSURE SENSOR/TRANSMISSION FLUID
TEMPERATURE THERMISTOR
21 - 198 AUTOMATIC TRANSMISSION - 48REDR
ELECTRONIC GOVERNOR (Continued)

(5) Slowly separate front of pan and reusable gas-
ket away from transmission allowing the fluid to
drain into drain pan.
(6) Hold up pan and remove remaining bolt hold-
ing pan to transmission.
(7) While holding pan level, lower pan and gasket
away from transmission.
(8) Pour remaining fluid in pan into drain pan.
(9) Remove screws holding filter to valve body
(Fig. 90).
(10) Separate filter from valve body and pour fluid
in filter into drain pan.
(11) Dispose of used trans fluid and filter properly.
INSTALLATION
(1) Position a new transmission oil filter onto the
valve body.
(2) Install the screws to hold the filter to the valve
body. Tighten the screws to 4 N´m (35 in.lbs.).
(3) Clean the gasket surfaces of the transmission
oil pan and transmission pan rail.
NOTE: The transmission pan oil gasket is reusable.
Inspect the sealing surfaces of the gasket. If the
sealing ribs on both surfaces appear to be in good
condition, clean the gasket of any foreign material
and reinstall.
(4) Position the oil pan gasket onto the oil pan.
(5) Position the oil pan and gasket onto the trans-
mission and install several bolts to hold the pan and
gasket to the transmission.(6) Install the remainder of the oil pan bolts.
Tighten the bolts to 13.6 N´m (125 in.lbs.).
(7) Lower vehicle and fill transmission. (Refer to
21 - TRANSMISSION/AUTOMATIC/FLUID - STAN-
DARD PROCEDURE)
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, add3
pints (1-1/2 quarts)of ATF +4 to transmission.
(b) If transmission was completely overhauled,
torque converter was replaced or drained, and
cooler was flushed, add12 pints (6 quarts)of ATF
+4 to transmission.
(3) Apply parking brakes.
(4) Start and run engine at normal curb idle
speed.
(5) Apply service brakes, shift transmission
through all gear ranges then back to NEUTRAL, set
parking brake, and leave engine running at curb idle
speed.
(6) Remove funnel, insert dipstick and check fluid
level. If level is low,add fluid to bring level to
MIN mark on dipstick.Check to see if the oil level
is equal on both sides of the dipstick. If one side is
noticably higher than the other, the dipstick has
picked up some oil from the dipstick tube. Allow the
oil to drain down the dipstick tube and re-check.
(7) Drive vehicle until transmission fluid is at nor-
mal operating temperature.
(8) With the engine running at curb idle speed, the
gear selector in NEUTRAL, and the parking brake
applied, check the transmission fluid level.
CAUTION: Do not overfill transmission, fluid foam-
ing and shifting problems can result.
(9) Add fluid to bring level up to MAX arrow
mark.
When fluid level is correct, shut engine off, release
park brake, remove funnel, and install dipstick in fill
tube.
Fig. 90 Transmission Filter
1 - TRANSMISSION
2 - FILTER
21 - 204 AUTOMATIC TRANSMISSION - 48REDR
FLUID AND FILTER (Continued)

KICKDOWN VALVE
When the throttle valve is as far over to the left as
it can go, the maximum line pressure possible will
enter the throttle pressure circuit. In this case, throt-
tle pressure will equal line pressure. With the kick-
down valve (Fig. 257) pushed into the bore as far as
it will go, fluid initially flows through the annular
groove of the 2-3 shift valve (which will be in the
direct drive position to the right).After passing the annular groove, the fluid is
routed to the spring end of the 2-3 shift valve. Fluid
pressure reacting on the area of land #1 overcomes
governor pressure, downshifting the 2-3 shift valve
into the kickdown, or second gear stage of operation.
The valve is held in the kickdown position by throttle
pressure routed from a seated check ball (#2). Again,
if vehicle speed is low enough, throttle pressure will
also push the 1-2 shift valve left to seat its governor
plug, and downshift to drive breakaway.
Fig. 257 Kickdown Valve - Wide Open Throttle
21 - 276 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)

2-3 SHIFT VALVE
The 2-3 shift valve mechanism (Fig. 263) consists
of the 2-3 shift valve, governor plug and spring, and
a throttle plug. After the 1-2 shift valve has com-
pleted its operation and applied the front band, line
pressure is directed to the 2-3 shift valve through the
connecting passages from the 1-2 shift valve. The line
pressure will then dead±end at land #2 until the 2-3
valve is ready to make its shift. Now that the vehicle
is in motion and under acceleration, there is throttle
pressure being applied to the spring side of the valve
and between lands #3 and #4.
As vehicle speed increases, governor pressure
increases proportionately, until it becomes great
enough to overcome the combined throttle and spring
pressure on the right side of the valve. Since the
throttle pressure end of the 2-3 shift valve is larger
in diameter than the 1-2 shift valve, the 2-3 shift will
always happen at a greater speed than the 1-2 shift.
When this happens, the governor plug is forced
against the shift valve moving it to the right. The
shift valve causes land #4 to close the passage sup-
plying throttle pressure to the 2-3 shift valve. With-
out throttle pressure present in the circuit now, the
governor plug will push the valve over far enough to
bottom the valve in its bore. This allows land #2 to
direct line pressure to the front clutch.
After the shift (Fig. 264), line pressure is directed
to the release side of the kickdown servo. This
releases the front band and applies the front clutch,shifting into third gear or direct drive. The rear
clutch remains applied, as it has been in the other
gears. During a manual ª1º or manual ª2º gear selec-
tion, line pressure is sent between the two lands of
the 2-3 governor plug. This line pressure at the gov-
ernor plug locks the shift valve into the second gear
position, preventing an upshift into direct drive. The
theory for the blocking of the valve is the same as
that of the 1-2 shift valve.
If the manual ª2º or manual ª1º gear position is
selected from the drive position, the PCM will control
the timing of the downshift by targeting for a high
governor pressure. When a safe vehicle speed is
reached, the PCM will switch to its normal control
governor curve and the downshift will occur.
3-4 SHIFT VALVE
The PCM energizes the overdrive solenoid during
the 3-4 upshift (Fig. 265). This causes the solenoid
check ball to close the vent port allowing line pres-
sure from the 2-3 shift valve to act directly on the 3-4
upshift valve. Line pressure on the 3-4 shift valve
overcomes valve spring pressure moving the valve to
the upshift position (Fig. 266). This action exposes
the feed passages to the 3-4 timing valve, 3-4 quick
fill valve, 3-4 accumulator, and ultimately to the
overdrive piston.
Fig. 263 2-3 Shift Valve - Before Shift
21 - 280 AUTOMATIC TRANSMISSION - 48REDR
VALVE BODY (Continued)