1998 DODGE RAM 1500 automatic transmission

OIL PUMP
DESCRIPTION
The oil pump (Fig. 109) is located in the pump
housing inside the bell housing of the transmission
case. The oil pump consists of an inner and outer
gear, a housing, and a reaction shaft support.
OPERATION
As the torque converter rotates, the converter hub
rotates the inner and outer gears. As the gears
rotate, the clearance between the gear teeth
increases in the crescent area, and creates a suction
at the inlet side of the pump. This suction draws
fluid through the pump inlet from the oil pan. As the
clearance between the gear teeth in the crescent area
decreases, it forces pressurized fluid into the pump
outlet and to the valve body.
Fig. 109 Oil Pump Assembly
1 - OIL SEAL 7 - BOLTS (6)
2 - VENT BAFFLE 8 - #1 THRUST WASHER (SELECTIVE)
3 - OIL PUMP BODY 9 - INNER GEAR
4 - GASKET 10 - OUTER GEAR
5 - REACTION SHAFT SUPPORT 11 - ªOº RING
6 - SEAL RINGS 12 - TORQUE CONVERTER SEAL RING
DRAUTOMATIC TRANSMISSION - 48RE 21 - 213

DISASSEMBLY
(1) Mark position of support in oil pump body for
assembly alignment reference. Use scriber or paint to
make alignment marks.
(2) Place pump body on two wood blocks.
(3) Remove reaction shaft support bolts and sepa-
rate support from pump body (Fig. 110).
(4) Remove pump inner and outer gears (Fig. 111).
(5) Remove o-ring seal from pump body (Fig. 112).
Discard seal after removal.
(6) Remove oil pump seal with Remover Tool
C-3981. Discard seal after removal.
CLEANING
Clean pump and support components with solvent
and dry them with compressed air.
INSPECTION
Check condition of the seal rings and thrust
washer on the reaction shaft support. The seal rings
do not need to be replaced unless cracked, broken, or
severely worn.
Inspect the pump and support components. Replace
the pump or support if the seal ring grooves or
machined surfaces are worn, scored, pitted, or dam-
aged. Replace the pump gears if pitted, worn
chipped, or damaged.
Inspect the pump bushing. Then check the reaction
shaft support bushing. Replace either bushing only if
heavily worn, scored or damaged. It is not necessary
to replace the bushings unless they are actually dam-
aged.
Clearance between outer gear and reaction shaft
housing should be 0.010 to 0.063 mm (0.0004 to
0.0025 in.). Clearance between inner gear and reac-
tion shaft housing should be 0.010 to 0.063 mm
(0.0004 to 0.0025 in.). Both clearances can be mea-sured at the same time by installing the gears in the
pump body and measure pump component clearances
as follows:
(1) Position an appropriate piece of PlastigageŸ
across both gears.
(2) Align the plastigage to a flat area on the reac-
tion shaft housing.
(3) Install the reaction shaft to the pump housing.
(4) Separate the reaction shaft housing from the
pump housing and measure the PlastigageŸ follow-
ing the instructions supplied with it.
Clearance between inner gear tooth and outer gear
should be 0.051 to 0.19 mm (0.002 to 0.0075 in.).
Measure clearance with an appropriate feeler gauge
(Fig. 113).
Clearance between outer gear and pump housing
should be 0.10 to 0.229 mm (0.004 to 0.009 in.). Mea-
sure clearance with an appropriate feeler gauge.
ASSEMBLY
(1) Lubricate pump gears with transmission fluid
and install them in pump body.
(2) Install thrust washer on reaction shaft support
hub. Lubricate washer with petroleum jelly or trans-
mission fluid before installation.
(3) If reaction shaft seal rings are being replaced,
install new seal rings on support hub. Lubricate seal
rings with transmission fluid or petroleum jelly after
installation. Squeeze each ring until ring ends are
securely hooked together.
Fig. 110 Reaction Shaft Support
1 - OIL PUMP
2 - REACTION SHAFT SUPPORT
Fig. 111 Pump Gears
1 - GEAR BORE
2 - PUMP BODY
3 - INNER GEAR
4 - OUTER GEAR
21 - 214 AUTOMATIC TRANSMISSION - 48REDR
OIL PUMP (Continued)

CAUTION: The reaction shaft support seal rings will
break if overspread, or twisted. If new rings are
being installed, spread them only enough for instal-
lation. Also be very sure the ring ends are securely
hooked together after installation. Otherwise, the
rings will either prevent pump installation, or break
during installation.
Fig. 112 Oil Pump Assembly
1 - OIL SEAL 7 - BOLTS (6)
2 - VENT BAFFLE 8 - #1 THRUST WASHER (SELECTIVE)
3 - OIL PUMP BODY 9 - INNER GEAR
4 - GASKET 10 - OUTER GEAR
5 - REACTION SHAFT SUPPORT 11 - ªOº RING
6 - SEAL RINGS 12 - TORQUE CONVERTER SEAL RING
Fig. 113 Checking Pump Gear Tip Clearance
1 - FEELER GAUGE
2 - INNER GEAR
3 - OUTER GEAR
DRAUTOMATIC TRANSMISSION - 48RE 21 - 215
OIL PUMP (Continued)

(4) Align and install reaction shaft support on
pump body.
(5) Install bolts attaching reaction shaft support to
pump. Tighten bolts to 20 N´m (175 in. lbs.) torque.
(6) Install new pump seal with Installer Tool
C-3860-A (Fig. 114). Use hammer or mallet to tap
seal into place.
(7) Install new o-ring on pump body. Lubricate oil
seal and o-ring with petroleum jelly.
(8) Cover pump assembly to prevent dust entry
and set aside for assembly installation.
OUTPUT SHAFT FRONT
BEARING
REMOVAL
(1) Remove overdrive unit from the vehicle.
(2) Remove overdrive geartrain from housing.
(3) Remove snap-ring holding output shaft front
bearing to overdrive geartrain. (Fig. 115).
(4) Pull bearing from output shaft.
INSTALLATION
(1) Place replacement bearing in position on
geartrain with locating retainer groove toward the
rear.
(2) Push bearing onto shaft until the snap-ring
groove is visible.
(3) Install snap-ring to hold bearing onto output
shaft.
(4) Install overdrive geartrain into housing.
(5) Install overdrive unit in vehicle.
OUTPUT SHAFT REAR
BEARING
REMOVAL
(1) Remove overdrive unit from the vehicle. (Refer
to 21 - TRANSMISSION/AUTOMATIC/OVERDRIVE
- REMOVAL)
(2) Remove overdrive geartrain from housing.
(3) Remove snap-ring holding output shaft rear
bearing into overdrive housing (Fig. 116).
(4) Using a suitable driver inserted through the
rear end of housing, drive bearing from housing.
Fig. 114 Oil Pump Seal
1 - SPECIAL TOOL C-3860-A
2 - PUMP BODY
3 - PUMP SEAL
Fig. 115 Output Shaft Front Bearing
1 - OUTPUT SHAFT FRONT BEARING
2 - SNAP-RING
3 - OUTPUT SHAFT
4 - GROOVE TO REAR
5 - OVERDRIVE GEARTRAIN
Fig. 116 Output Shaft Rear Bearing
1 - OUTPUT SHAFT REAR BEARING
2 - OVERDRIVE HOUSING
3 - SNAP-RING
21 - 216 AUTOMATIC TRANSMISSION - 48REDR
OIL PUMP (Continued)

INSTALLATION
(1) Place replacement bearing in position in hous-
ing.
(2) Using a suitable driver, drive bearing into
housing until the snap-ring groove is visible.
(3) Install snap-ring to hold bearing into housing
(Fig. 116).
(4) Install overdrive geartrain into housing.
(5) Install overdrive unit in vehicle.
OVERDRIVE CLUTCH
DESCRIPTION
The overdrive clutch (Fig. 117) is composed of the
pressure plate, clutch plates, holding discs, overdrive
piston retainer, piston, piston spacer, and snap-rings.
The overdrive clutch is the forwardmost component
in the transmission overdrive unit and is considered
a holding component. The overdrive piston retainer,
piston, and piston spacer are located on the rear of
the main transmission case.
NOTE: The number of discs and plates may vary
with each engine and vehicle combination.
OPERATION
To apply the clutch, pressure is applied between
the piston retainer and piston. The fluid pressure is
provided by the oil pump, transferred through the
control valves and passageways, and enters the
clutch through passages at the lower rear portion of
the valve body area. With pressure applied between
the piston retainer and piston, the piston moves
away from the piston retainer and compresses the
clutch pack. This action applies the clutch pack,
allowing torque to flow through the intermediate
shaft into the overdrive planetary gear set. The over-
drive clutch discs are attached to the overdrive clutch
hub while the overdrive clutch plates, reaction plate,
and pressure plate are lugged to the overdrive hous-
ing. This allows the intermediate shaft to transfer
the engine torque to the planetary gear and overrun-
ning clutch. This drives the planetary gear inside the
annulus, which is attached to the overdrive clutch
drum and output shaft, creating the desired gear
ratio. The waved snap-ring is used to cushion the
application of the clutch pack for the 5 disc version of
the overdrive clutch. The 6 disc overdrive clutch does
not use a waved snap-ring.
Fig. 117 Overdrive Clutch
1 - REACTION PLATE 2 - PRESSURE PLATE
DRAUTOMATIC TRANSMISSION - 48RE 21 - 217
OUTPUT SHAFT REAR BEARING (Continued)

OVERDRIVE UNIT
REMOVAL
(1) Shift transmission into PARK.
(2) Raise vehicle.
(3) Remove transfer case, if equipped.
(4) Mark propeller shaft universal joint(s) and axle
pinion yoke, or the companion flange and flange
yoke, for alignment reference at installation, if neces-
sary.
(5) Disconnect and remove the rear propeller shaft,
if necessary. (Refer to 3 - DIFFERENTIAL & DRIV-
ELINE/PROPELLER SHAFT/PROPELLER SHAFT -
REMOVAL)
(6) Remove transmission oil pan, remove gasket,
drain oil and reinstall pan.
(7) If overdrive unit had malfunctioned, or if fluid
is contaminated, remove entire transmission. If diag-
nosis indicated overdrive problems only, remove just
the overdrive unit.
(8) Support transmission with transmission jack.
(9) Remove bolts attaching overdrive unit to trans-
mission (Fig. 118).
CAUTION: Support the overdrive unit with a jack
before moving it rearward. This is necessary to pre-
vent damaging the intermediate shaft. Do not allow
the shaft to support the entire weight of the over-
drive unit.
(10) Carefully work overdrive unit off intermediate
shaft. Do not tilt unit during removal. Keep it as
level as possible.(11) If overdrive unit does not require service,
immediately insert Alignment Tool 6227-2 in splines
of planetary gear and overrunning clutch to prevent
splines from rotating out of alignment. If misalign-
ment occurs, overdrive unit will have to be disassem-
bled in order to realign splines.
(12) Remove and retain overdrive piston thrust
bearing. Bearing may remain on piston or in clutch
hub during removal.
(13) Position drain pan on workbench.
(14) Place overdrive unit over drain pan. Tilt unit
to drain residual fluid from case.
(15) Examine fluid for clutch material or metal
fragments. If fluid contains these items, overhaul will
be necessary.
(16) If overdrive unit does not require any service,
leave alignment tool in position. Tool will prevent
accidental misalignment of planetary gear and over-
running clutch splines.
DISASSEMBLY
(1) Remove transmission speed sensor and o-ring
seal from overdrive case (Fig. 119).
(2) Remove overdrive piston thrust bearing (Fig.
120).
Fig. 118 Overdrive Unit Bolts
1 - OVERDRIVE UNIT
2 - ATTACHING BOLTS (7)
Fig. 119 Transmission Speed Sensor
1 - SOCKET AND WRENCH
2 - SPEED SENSOR
3 - O-RING
21 - 218 AUTOMATIC TRANSMISSION - 48REDR

OVERDRIVE PISTON
(1) Remove overdrive piston thrust plate (Fig.
121). Retain thrust plate. It is a select fit part and
may possibly be reused.(2) Remove intermediate shaft spacer (Fig. 122).
Retain spacer. It is a select fit part and may possibly
be reused.
(3) Remove overdrive piston from retainer (Fig.
123).
Fig. 120 Overdrive Piston Thrust Bearing Removal/
Installation
1 - THRUST BEARING
2 - OVERDRIVE PISTON
3 - THRUST PLATE
Fig. 121 Overdrive Piston Thrust Plate Removal/
Installation
1 - OVERDRIVE PISTON
2 - OVERDRIVE PISTON SPACER (SELECT FIT)
Fig. 122 Intermediate Shaft Spacer Location
1 - INTERMEDIATE SHAFT
2 - INTERMEDIATE SHAFT SPACER (SELECT FIT)
Fig. 123 Overdrive Piston Removal
1 - PISTON RETAINER
2 - OVERDRIVE PISTON
DRAUTOMATIC TRANSMISSION - 48RE 21 - 219
OVERDRIVE UNIT (Continued)

OVERDRIVE CLUTCH PACK
(1) Remove overdrive clutch pack wire retaining
ring (Fig. 124).
(2) Remove overdrive clutch pack (Fig. 125).
(3) Note position of clutch pack components for
assembly reference (Fig. 126).
OVERDRIVE GEARTRAIN
(1) Remove overdrive clutch wave spring (Fig.
127), 5 disc clutch only.
(2) Remove overdrive clutch reaction snap-ring
(Fig. 128). Note that snap-ring is located in same
groove as wave spring.
Fig. 124 Removing Overdrive Clutch Pack Retaining
Ring
1 - OVERDRIVE CLUTCH PACK RETAINING RING
Fig. 125 Overdrive Clutch Pack Removal
1 - OVERDRIVE CLUTCH PACK
Fig. 126 Overdrive Clutch Component Position -
Typical
1 - REACTION PLATE
2 - CLUTCH PLATES
3 - PRESSURE PLATE
4 - CLUTCH DISCS
Fig. 127 Overdrive Clutch Wave Spring Removal - 5
Disc Clutch Only
1 - WAVE SPRING
Fig. 128 Overdrive Clutch Reaction Snap-Ring
Removal
1 - REACTION RING
2 - CLUTCH HUB
21 - 220 AUTOMATIC TRANSMISSION - 48REDR
OVERDRIVE UNIT (Continued)