CONDITION POSSIBLE CAUSES CORRECTION
SLIPS IN OVERDRIVE
FOURTH GEAR1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Overdrive Clutch Pack Worn. 2. Remove overdrive unit and rebuild clutch
pack.
3. Overdrive Piston Retainer Bleed
Orifice Blown Out.3. Disassemble transmission, remove
retainer and replace orifice.
4. Overdrive Piston or Seal
Malfunction.4. Remove overdrive unit. Replace seals if
worn. Replace piston if damaged. If piston
retainer is damaged, remove and
disassemble the transmission.
5. 3-4 Shift Valve, Timing Valve or
Accumulator Malfunction.5. Remove and overhaul valve body.
Replace accumulator seals. Make sure all
valves operate freely in bores and do not
bind or stick. Make sure valve body screws
are correctly tightened and separator plates
are properly positioned.
6. Overdrive Unit Thrust Bearing
Failure.6. Disassemble overdrive unit and replace
thrust bearing (NO. 1 thrust bearing is
between overdrive piston and clutch hub;
NO. 2 thrust bearing is between the
planetary gear and the direct clutch spring
plate; NO. 3 thrust bearing is between
overrunning clutch hub and output shaft).
7. O/D Check Valve/Bleed Orifice
Failure.7. Check for function/secure orifice insert in
O/D piston retainer.
DELAYED 3-4 UPSHIFT
(SLOW TO ENGAGE)1. Fluid Level Low. 1. Add fluid and check for leaks.
2. Throttle Valve Cable Mis-adjusted. 2. Adjust throttle valve cable.
3. Overdrive Clutch Pack Worn/
Burnt.3. Remove unit and rebuild clutch pack.
4. TPS Faulty. 4. Test with DRBTscan tool and replace as
necessary
5. Overdrive Clutch Bleed Orifice
Plugged.5. Disassemble transmission and replace
orifice.
6. Overdrive Solenoid or Wiring
Shorted/Open.6. Test solenoid and check wiring for
loose/corroded connections or shorts/
grounds. Replace solenoid if faulty and
repair wiring if necessary.
7. Overdrive Excess Clearance. 7. Remove unit. Measure end play and
select proper spacer.
8. O/D Check Valve Missing or
Stuck.8. Check for presence of check valve.
Repair or replace as required.
TORQUE CONVERTER
LOCKS UP IN SECOND
AND/OR THIRD GEARLockup Solenoid, Relay or Wiring
Shorted/Open.Test solenoid, relay and wiring for
continuity, shorts or grounds. Replace
solenoid and relay if faulty. Repair wiring
and connectors as necessary.
HARSH 1-2, 2-3, 3-4 OR
3-2 SHIFTSLockup Solenoid Malfunction. Remove valve body and replace solenoid
assembly.
DRAUTOMATIC TRANSMISSION - 48RE 21 - 155
AUTOMATIC TRANSMISSION - 48RE (Continued)
(a) Start park rod into park pawl. If rod will not
slide past park pawl, pawl is engaged in park gear.
Rotate overdrive output shaft with suitable size 12
point socket; this will free pawl and allow rod to
engage.
(b) Align and seat valve body on case. Be sure
manual lever shaft and overdrive connector are
fully seated in case.
(c) Install and start all valve body attaching
bolts by hand. Then tighten bolts evenly, in a diag-
onal pattern to 12 N´m (105 in. lbs.) torque.Do
not overtighten valve body bolts. This could
result in distortion and cross leakage after
installation..
(5) Install new filter on valve body. Tighten filter
screws to 4 N´m (35 in. lbs.).
CAUTION: If the condition of the transmission
before the overhaul procedure caused excessive
metallic or fiber contamination in the fluid, replace
the torque converter and reverse flush the cooler(s)
and cooler lines. Fluid contamination and transmis-
sion failure can result if not done.(6) Move the transmission manual shaft lever to
the manual LOW position.
(7) Install the TRS mounting bracket into the
transmission case. Using Adapter 8581 (Fig. 60),
tighten the mounting bracket to 34 N´m (300 in.lbs.).
(8) Install the TRS (Fig. 61) into the mounting
bracket with the wiring connector facing the front of
the transmission.
Fig. 58 Accumulator Piston And Springs
1 - ACCUMULATOR PISTON
2 - OUTER SPRING
3 - INNER SPRING
Fig. 59 Manual Lever Shaft Seal
1 - 15/1688SOCKET
2 - SEAL
Fig. 60 Tighten the TRS Mounting Bracket
1 - SOLENOID CASE CONNECTOR
2 - TRS MOUNTING BRACKET
3 - ADAPTER 8581
Fig. 61 Remove Transmission Range Sensor
1 - SOLENOID CASE CONNECTOR
2 - TRS MOUNTING BRACKET
3 - TRANSMISSION RANGE SENSOR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 173
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)
(4) Lower the vehicle.
(5) Remove the dash panel insulation pad as nec-
essary to access the gearshift cable grommet (Fig.
104).
(6) Remove grommet from the dash panel.
(7) Remove any steering column trim necessary to
access the gearshift cable and BTSI mechanism.
(8) Disconnect the BTSI wiring connector.
(9) Disconnect cable at lower column bracket and
shift lever pin and pull the cable through the dash
panel opening into the vehicle (Fig. 105).
(10) Remove gearshift cable from vehicle.INSTALLATION
(1) Route the transmission end of the gearshift
cable through the opening in the dash panel (Fig.
106).
(2) Seat the cable grommet into the dash panel
opening.
(3) Snap the cable into the steering column
bracket so the retaining ears (Fig. 107) are engaged
and snap the cable eyelet onto the shift lever ball
stud.
(4) Raise the vehicle.
(5) Place the transmission manual shift lever in
the ªPARKº detent (rearmost) position and rotate
prop shaft to ensure transmission is in PARK.
Fig. 104 Gearshift Cable at the Dash Panel
1 - GEARSHIFT CABLE
2 - GROMMET
Fig. 105 Gearshift Cable at Steering Column
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
Fig. 106 Gearshift Cable at the Dash Panel
1 - GEARSHIFT CABLE
2 - GROMMET
Fig. 107 Gearshift Cable at Steering Column
1 - STEERING COLUMN
2 - GEARSHIFT CABLE
3 - GEARSHIFT CABLE LOCK TAB
4 - BTSI SOLENOID LOCK TAB
5 - BTSI CONNECTOR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 211
GEARSHIFT CABLE (Continued)
INSTALLATION
(1) Be sure overdrive unit Alignment Tool 6227-2
is fully seated before moving unit. If tool is not
seated and gear splines rotate out of alignment, over-
drive unit will have to be disassembled in order to
realign splines.
(2) If overdrive piston retainer was not removed
during service and original case gasket is no longer
reusable, prepare new gasket by trimming it.
(3) Cut out old case gasket around piston retainer
with razor knife (Fig. 176).
(4) Use old gasket as template and trim new gas-
ket to fit.
(5) Position new gasket over piston retainer and
on transmission case. Use petroleum jelly to hold
gasket in place if necessary. Do not use any type of
sealer to secure gasket. Use petroleum jelly only.
(6) Install selective spacer on intermediate shaft, if
removed. Spacer goes in groove just rearward of
shaft rear splines (Fig. 177).
(7) Install thrust bearing in overdrive unit sliding
hub. Use petroleum jelly to hold bearing in position.
CAUTION: Be sure the shoulder on the inside diam-
eter of the bearing is facing forward.(8) Verify that splines in overdrive planetary gear
and overrunning clutch hub are aligned with Align-
ment Tool 6227-2. Overdrive unit cannot be installed
if splines are not aligned. If splines have rotated out
of alignment, unit will have to be disassembled to
realign splines.
(9) Carefully slide Alignment Tool 6227-2 out of
overdrive planetary gear and overrunning clutch
splines.
(10) Raise overdrive unit and carefully slide it
straight onto intermediate shaft. Insert park rod into
park lock reaction plug at same time. Avoid tilting
overdrive during installation as this could cause
planetary gear and overrunning clutch splines to
rotate out of alignment. If this occurs, it will be nec-
essary to remove and disassemble overdrive unit to
realign splines.
(11) Work overdrive unit forward on intermediate
shaft until seated against transmission case.
(12) Install bolts attaching overdrive unit to trans-
mission unit. Tighten bolts in diagonal pattern to 34
N´m (25 ft-lbs).
(13) Connect the transmission speed sensor and
overdrive wiring connectors.
(14) Install the transfer case, if equipped.
(15) Align and install rear propeller shaft, if nec-
essary. (Refer to 3 - DIFFERENTIAL & DRIVELINE/
PROPELLER SHAFT/PROPELLER SHAFT -
INSTALLATION)
Fig. 176 Trimming Overdrive Case Gasket
1 - GASKET
2 - SHARP KNIFE
Fig. 177 Intermediate Shaft Selective Spacer
Location
1 - SELECTIVE SPACER
2 - SPACER GROOVE
3 - INTERMEDIATE SHAFT
DRAUTOMATIC TRANSMISSION - 48RE 21 - 235
OVERDRIVE UNIT (Continued)
OPERATION
At key-on, overdrive operation is allowed. Pressing
the switch once causes the tow/haul overdrive OFF
mode to be entered and the Tow/Haul lamp to be illu-
minated. Pressing the switch a second time causes
normal overdrive operation to be restored and the
tow/haul lamp to be turned off. The tow/haul over-
drive OFF mode defaults to ON after the ignition
switch is cycled OFF and ON. The normal position
for the control switch is the ON position. The switch
must be in this position to energize the solenoid and
allow a 3-4 upshift. The control switch indicator light
illuminates only when the tow/haul overdrive switch
is turned to the OFF position, or when illuminated
by the transmission control module.
DIAGNOSIS AND TESTING - OVERDRIVE
ELECTRICAL CONTROLS
The tow/haul overdrive off switch, valve body sole-
noid, case connectors and related wiring can all be
tested with a 12 volt test lamp or a volt/ohmmeter.
Check continuity of each component when diagnosis
indicates this is necessary.
Switch and solenoid continuity should be checked
whenever the transmission fails to shift into fourth
gear range.
REMOVAL
(1) Using a plastic trim tool, remove the tow/haul
overdrive off switch retainer from the shift lever (Fig.
237).(2) Pull the switch outwards to release it from the
connector in the lever (Fig. 238)
INSTALLATION
NOTE: There is enough slack in the wire to pull out
the connector from the lever.
(1) Pull the connector out of the lever just enough
to grasp it.
CAUTION: Be careful not to bend the pins on the
tow/haul overdrive off switch. Use care when
installing the switch, as it is not indexed, and can
be accidentally installed incorrectly.
(2) Install the tow/haul overdrive off switch into
the connector (Fig. 239)
(3) Push the tow/haul overdrive off switch and wir-
ing into the shift lever.
(4) Install the tow/haul overdrive off switch
retainer onto the shift lever.
Fig. 237 Tow/Haul Overdrive Off Switch Retainer
Fig. 238 Remove the Tow/Haul Overdrive Off Switch
Fig. 239 Install the Tow/Haul Overdrive Off Switch
21 - 262 AUTOMATIC TRANSMISSION - 48REDR
TOW/HAUL OVERDRIVE SWITCH (Continued)
Indicated Gear Position Transmission
StatusColumn Shifter
Position
Mechanical State Electronic Display
(Ignition Unlocked)Electronic Display
(Ignition On)
P P P Vehicle is in PARK
with the pawl
engaged.In the PARK gate.
R The PARK pawl is
disengaged and the
vehicle is free to
roll, but REVERSE
is not engaged.Between the PARK
and REVERSE
gates.
R R R The transmission is
hydraulically in
REVERSE.In the REVERSE
gate.
N The transmission is
transitioning
between REVERSE
and NEUTRAL.Between the
REVERSE and
NEUTRAL gates.
N N N The vehicle is in
NEUTRAL.In the NEUTRAL
gate.
N The transmission is
transitioning
between NEUTRAL
and DRIVE, but is
not in DRIVE.Between the
NEUTRAL and
DRIVE gates.
D D D The transmission is
hydraulically in
DRIVE.In the DRIVE gate,
2 2 2 The transmission is
hydraulically in
Manual SECOND.In the SECOND
gate.
1 1 1 The transmission is
hydraulically in
Manual FIRST.In the FIRST gate.
DIAGNOSIS AND TESTING - TRANSMISSION
RANGE SENSOR (TRS)
NOTE: For all circuit identification in the following
steps, Refer to the appropriate Wiring Information.
(1) Raise vehicle on suitable hoist.
(2) Disconnect the vehicle's shift cable from the
manual lever.
(3) With the manual lever in the PARK position
(the PARK position is with the manual lever moved
to the full rearward position), measure the resistance
between the Park/Neutral Position Sense pin of the
TRS and the transmission case. The resistance
should be less than 5 ohms.
(4) With the manual lever in the NEUTRAL posi-
tion (the NEUTRAL position is with the manuallever moved two detents forward of the full rearward
position), measure the resistance between the Park/
Neutral Position Sense pin of the TRS and the trans-
mission case. The resistance should be less than 5
ohms.
(5) If the resistance is greater than 5 ohms in
either of the previous steps, check for a dirty contact
between the tip of the TRS rod and the valve body
manual lever. If the contact is OK, replace the TRS.
(6) With the manual lever in the REVERSE posi-
tion (the REVERSE position is with the manual lever
moved one detent forward of the full rearward posi-
tion), measure the resistance between the Fused
Ignition Switch Output and the Back-up Lamp feed
pins of the TRS. The resistance should be less than 5
ohms. If the resistance is greater than 5 ohms,
replace the TRS.
21 - 264 AUTOMATIC TRANSMISSION - 48REDR
TRANSMISSION RANGE SENSOR (Continued)
(7) With the manual lever in the PARK position
(the PARK position is with the manual lever moved
to the full rearward position), measure the resistance
between the Transmission Range Sensor MUX and
the Transmission Range Sensor 5V Supply pins of
the TRS. The resistance should be 522.2 ohms. If the
resistance is not correct, replace the TRS.
(8) With the manual lever in the REVERSE posi-
tion (the REVERSE position is with the manual lever
moved one detent forward of the full rearward posi-
tion), measure the resistance between the Transmis-
sion Range Sensor MUX and the Transmission Range
Sensor 5V Supply pins of the TRS. The resistance
should be 206.2 ohms. If the resistance is not correct,
replace the TRS.
(9) With the manual lever in the NEUTRAL posi-
tion (the NEUTRAL position is with the manual
lever moved two detents forward of the full rearward
position), measure the resistance between the Trans-
mission Range Sensor MUX and the Transmission
Range Sensor 5V Supply pins of the TRS. The resis-
tance should be 108.6 ohms. If the resistance is not
correct, replace the TRS.
(10) With the manual lever in the DRIVE position
(the DRIVE position is with the manual lever moved
three detents forward of the full rearward position),
measure the resistance between the Transmission
Range Sensor MUX and the Transmission Range
Sensor 5V Supply pins of the TRS. The resistance
should be 59.9 ohms. If the resistance is not correct,
replace the TRS.
(11) With the manual lever in the SECOND posi-
tion (the SECOND position is with the manual lever
moved one detent rearward of the full forward posi-
tion), measure the resistance between the Transmis-
sion Range Sensor MUX and the Back-up Lamp feed
pins of the TRS. The resistance should be 31.9 ohms.
If the resistance is not correct, replace the TRS.
(12) With the manual lever in the LOW position
(the LOW position is with the manual lever moved to
the full forward position), measure the resistance
between the Transmission Range Sensor MUX and
the Back-up Lamp feed pins of the TRS. The resis-
tance should be 13.7 ohms. If the resistance is not
correct, replace the TRS.
REMOVAL
(1) Raise vehicle and position drain pan under the
transmission range sensor (TRS).
(2) Move the transmission manual lever to the
manual LOW position. The manual LOW position is
with the manual lever in the forward-most detent.(3) Disengage the wiring connector from the TRS.
(4) Remove the two screws holding the TRS to the
TRS mounting bracket.
(5) Remove the TRS (Fig. 242) from the TRS
mounting bracket by pulling it straight out of the
bracket.
(6) Loosen the TRS mounting bracket in the trans-
mission case using Adapter 8581 (Fig. 243).
Fig. 242 Remove Transmission Range Sensor
1 - SOLENOID CASE CONNECTOR
2 - TRS MOUNTING BRACKET
3 - TRANSMISSION RANGE SENSOR
Fig. 243 Loosen the TRS Mounting Bracket
1 - SOLENOID CASE CONNECTOR
2 - TRS MOUNTING BRACKET
3 - ADAPTER 8581
DRAUTOMATIC TRANSMISSION - 48RE 21 - 265
TRANSMISSION RANGE SENSOR (Continued)