33. Remove all bolts (1) holding the transmission (3)
to the engine adapter (2), gas engines.
34. Carefully work transmission and torque converter
assembly rearward off engine block dowels.
35. Lower transmission and remove assembly from
under the vehicle.
36. To remove torque converter, remove C-clamp
from edge of bell housing and carefully slide
torque converter out of the transmission.
DISASSEMBLY
1. Clean exterior of transmission with suitable solvent
or pressure washer.
2. Place transmission in vertical position.
3. Measure the input shaft end play as follows.
a. Attach Adapter 8266-5 (2) to Handle 8266-8
(1).
b. Attach Dial Indicator C-3339 (3) to Handle
8266-8 (1).
c. Install the assembled tool onto the input shaft
of the transmission and tighten the retaining
screw on Adapter 8266-5 to secure it to the
input shaft.
d. Position the dial indicator plunger against a flat
spot on the oil pump and zero the dial indica-
tor.
e. Move input shaft in and out and record read-
ing. Record the maximum travel for assembly
reference
32. Remove rear band adjusting lever and reaction
pin.
33. Remove rear band.
34. Compress front servo rod guide (2) with large
C-clamp (1) and Tool C-4470 (4), or Compressor
Tool C-3422-B. Compress guide only enough to
permit snap-ring removal (about 1/8 in.).
35. Remove servo piston snap-ring (4). Unseat one
end of ring. Then carefully work removal tool
around back of ring until free of ring groove.Exer-
cise caution when removing snap-ring. Servo
bore can be scratched or nicked if care is not
exercised.
36. Remove tools and remove rear servo retainer (3),
spring and piston assembly.
CLEANING
Clean the case in a solvent tank. Flush the case bores and fluid passages thoroughly with solvent. Dry the case and
all fluid passages with compressed air. Be sure all solvent is removed fromthe case and that all fluid passages are
clear.
NOTE: Do not use shop towels or rags to dry the case (or any other transmission component) unless they
aremadefromlint-freematerials.Lintwillsticktocasesurfacesandtransmission components and circu-
late throughout the transmission after assembly. A sufficient quantity of lint can block fluid passages and
interfere with valve body operation.
Lubricate transmission parts with Mopar
ATF +4, Automatic Transmission fluid, during overhaul and assembly. Use
petroleum jelly to prelubricate seals, O-rings, and thrust washers. Petroleumjellycanalsobeusedtoholdpartsin
place during reassembly.
INSPECTION
Inspect the case for cracks, porous spots, worn bores, or damaged threads.Damaged threads can be repaired with
Helicoil thread inserts. However, the case will have to be replaced if it exhibits any type of damage or wear.
Lubricate the front band adjusting screw threads with petroleum jelly andthread the screw part-way into the case.
Be sure the screw turns freely.
Inspect the transmission bushings during overhaul. Bushing condition isimportant as worn, scored bushings con-
tribute to low pressures, clutch slipand accelerated wear of other components. However, do not replace bushings
as a matter of course. Replace bushings only when they are actually worn, orscored.
Component Metric Inch
Overdrive piston thrust plate Thrust plate and
spacer are select fit.
Refer to size charts
and selection
procedures in
Overdrive Unit D&A
procedures Intermediateshaft spacer
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.
Rearservo 1range Nomorethan21kPa(3psi)lowerthanlinepressure.
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
andreturnto0-7kPa(0-1.5psi)whenstoppedwith
transmission in D, 1, 2. Pressure above 7 kPa (1.5 psi)
at stand still will prevent transmission from
downshifting.
TORQUE SPECIFICATIONS
DESCRIPTION Nꞏm Ft. Lbs. In. Lbs.
Fitting, cooler line at trans 18 13 -
Bolt, torque convertor 47 35 -
Bolt, clevis bracket to
crossmember47 35 -
Bolt, clevis bracket to rear
support68 50 -
Bolt, driveplate to
crankshaft75 55 -
Bolt, Transmission Throttle
Va l v e A c t u a t o r8.5 - 75
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
cam17 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 -
SPECIAL TOOLS
RE TRANSMISSION
Pilot Studs C-3288-B
Oil Pressure Gauge - C-3292
Pressure Gauge - C-3293SP
Dial Indicator C-3339
Valve Spring Compressor C-3422-B
Adapter, Band Adjuster - C-3705
Puller/Slide Hammer, C-3752
Gauge, Throttle Setting - C-3763
Installer C-3860-A
Spring Compressor - C-3863-A
OPERATION
Both the accumulator and the 3-4 accumulator func-
tion the same. Line pressure (1) is directed to the
small end of the piston when the transmission is
placed into a DRIVE position, bottoming it against the
accumulator plate.
Diesel version shown.
When the 1-2 upshift occurs, line pressure (2) is
directed to the large end of the piston and then to the
kickdown servo. As the line pressure reaches the
accumulator, the combination of spring pressure and
line pressure forces the piston away from the accumu-
lator plate. This causes a balanced pressure situation,
which results in a cushioned band application. After
the kickdown servo has become immovable, line pres-
sure will finish pushing the accumulator up into its
bore (1). When the large end of the accumulator pis-
ton is seated in its bore, the band or clutch is fully
applied.
NOTE: The accumulator is shown in the inverted
position for illustrative purposes.
INSPECTION
Inspect the accumulator piston and seal rings. Replace the seal rings if worn or cut. Replace the piston if chipped
or cracked.
Check condition of the accumulator inner and outer springs. Replace the springs if the coils are cracked, distorted
or collapsed.
OPERATION
Compensation is required for performance variations 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 manufacturing 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 absence of 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 thetransducer signal isnecessary 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, how-
ever 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 offset during the
coldperiod of operation.
GOVERNOR PRESSURE SOLENOID VALVE
The inlet side of the solenoid valve is exposed to normal transmission linepressure. The outlet side of the valve
leads to the valve body governor circuit.
The solenoid valve regulates line pressure to produce governor pressure.Theaveragecurrentsuppliedtothesole-
noid controls governor pressure. One amp current produces zero kPa/psi governor pressure. Zero amps sets the
maximum governor pressure.
The powertrain control module (PCM) turns on the trans control relay whichsupplies electrical power to the solenoid
valve. Operating voltage is 12 volts (DC). The PCM controls the ground sideof the solenoid using the governor
pressure solenoidcontrol circuit.
GOVERNOR PRESSURE SENSOR
The sensor output signal provides the necessary feedback to the PCM. This feedback is needed to adequately
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 gov-
ernor pressure.
GOVERNOR PRESSURE CURVES
LOW TRANSMISSION FLUID TEMPERATURE
When the transmission fluid is cold the conventional governor can delay shifts, resulting in higher than normal shift
speeds and harsh shifts. The electronically controlled low temperature governor pressure curve is higher than nor-
mal to make the transmission shift at normal speeds and sooner. The PCM usesa temperature sensor in the trans-
mission oil sump to determine when low temperature governor pressure is needed.
NORMAL OPERATION
Normal operation is refined through the increased computing power of the PCM and through access to data on
engine operating conditions provided by the PCM that were not available with the previous stand-alone electronic
module. This facilitated the development of a load adaptive shift strategy - the ability to alter the shift schedule in
response to vehicle load condition. One manifestation of this capabilityis grade
huntingprevention - the ability of
the transmission logic to delay an upshift on a grade if the engine does not have sufficient power to maintain speed
in the higher gear. The 3-2 downshift and the potential for hunting betweengears occurs with a heavily loaded
vehicle or on steep grades. When hunting occurs, it is very objectionable because shifts are frequent and accom-
panied by large changes in noise and acceleration.
FLUID AND FILTER
DIAGNOSIS AND TESTING
EFFECTS OF INCORRECT FLUID LEVEL
Alowfluidlevelallowsthepumptotakeinairalongwiththefluid.Airinthe fluid will cause fluid pressures to be
low and develop slower than normal. If the transmission is overfilled, thegears churn the fluid into foam. This aer-
ates the fluid and causing the same conditions occurring with a low level. In either case, air bubbles cause fluid
overheating, oxidation, and varnish buildup which interferes with valveand clutch operation. Foaming also causes
fluid expansion which can result in fluid overflow from the transmission vent or fill tube. Fluid overflow can easily be
mistaken for a leak if inspection is not careful.
CAUSES OF BURNT FLUID
Burnt, discolored fluid is a result of overheating which has two primary causes.
1. A result of restricted fluid flow through the main and/or auxiliary cooler. This condition is usually the result of a
faulty or improperly installed drainback valve, a damaged oil cooler, or severe restrictions in the coolers and lines
caused by debris or kinked lines.
2. Heavy duty operation with a vehicle not properly equipped for this type of operation. Trailer towing 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 system,and the engine/axle ratio combination
needed to handle heavy loads.
FLUID CONTAMINATION
Transmission fluid contamination is generally a result of:
adding incorrect fluid
failure to clean dipstick and fill tube when checking level
engine coolant entering the fluid
internal failure that generates debris
overheat that generates sludge (fluid breakdown)
failure to replace contaminated converter after repair
The use of non-recommended fluids can result in transmission failure. Theusual results are erratic shifts, slippage,
abnormal wear and eventual failure due to fluid breakdown and sludge formation. Avoid this condition by using rec-
ommended fluids only.
The dipstick cap and fill tube should be wiped clean before checking fluid level. Dirt, grease and other foreign mate-
rial 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 withdrawing the dipstick.
Engine coolant in the transmission fluid is generally 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 whenever a failure generatessludge and debris. This is necessary
because normal converter flushing procedures will not remove all contaminants.
STANDARD PROCEDURE
FLUID LEVEL CHECK
Low fluid level can cause a variety of conditions because it allows the pumpto 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 conditions 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 nor-
mal valve, clutch, and accumulator operation. Foaming can also result in fluid escaping from the transmission vent
where it may be mistaken for a leak.
CLUTCH-FRONT
DESCRIPTION
The front clutch assembly is composed of the front clutch retainer (11), pressure plate, clutch plates (4), clutch discs
(7), clutch piston (2), clutch piston return spring (9), clutch piston spring retainer (3), and snap-rings (5, 8). The front
clutch is the forward-most component in the transmission geartrain and isdirectly behind the oil pump and is con-
sidered a driving component.
OPERATION
To apply the clutch, pressure is applied between the clutch retainer and piston. The fluid pressure is provided by the
oil pump, transferred through the control valves and passageways, and enters the clutch through the hub of the
reaction shaft support. With pressure applied between the clutch retainer and piston, the piston moves away from
the clutch retainer and compresses the clutch pack. This action applies the clutch pack, allowing torque to flow
through the input shaft into the driving discs, and into the clutch plates and pressure plate that are lugged to the
clutch retainer. The waved snap-ring is used to cushion the application ofthe clutch pack.
When pressure is released from the piston, the spring returns the piston toits fully released position and disen-
gages the clutch. The release spring also helps to cushion the applicationof the clutch assembly. When the clutch
is in the process of being released by the release spring, fluid flows through a vent and one-way ball-check-valve
located in the clutch retainer. The check-valve is needed to eliminate thepossibility of plate drag caused by cen-
trifugal force acting on the residual fluid trapped in the clutch piston retainer.
48RE Front Clutch Components
1 - INNER PISTON SEAL 7 - CLUTCH DISCS
2 - CLUTCH PISTON 8 - RETAINER SNAP-RING
3 - CLUTCH PISTON SPRING RETAINER 9 - CLUTCH PISTON SPRINGS
4 - CLUTCH PLATES 10 - OUTER PISTON SEAL
5 - CLUTCH PACK SNAP-RING (WAVED) 11 - FRONT CLUTCH RETAINER
6 - REACTION PLATE