2003 DODGE RAM Service Repair Manual

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Page 2257 of 2895

DODGE RAM 2003 Service Repair Manual (13) Install new gasket at rear of transmission
case. Use petroleum jelly to hold gasket in place. Be
sure to align governor feed holes in gasket with feed
passages in case (Fig. 192). Also install ga

(13) Install new gasket at rear of transmission
case. Use petroleum jelly to hold gasket in place. Be
sure to align governor feed holes in gasket with feed
passages in case (Fig. 192). Also install gasket before
overdrive piston retainer. Center hole in gasket is
smaller than retainer and cannot be installed over
retainer.
(14) Position overdrive piston retainer on trans-
mission case and align bolt holes in retainer, gasket
and case (Fig. 193). Then install and tighten retainer
bolts to 17 N´m (13 ft. lbs.) torque.
(15) Install new seals on overdrive piston.
(16) Stand transmission case upright on bellhous-
ing.
(17) Position Guide Ring 8114-1 on outer edge of
overdrive piston retainer.
(18) Position Seal Guide 8114-3 on inner edge of
overdrive piston retainer.
(19) Install overdrive piston in overdrive piston
retainer by: aligning locating lugs on overdrive piston
to the two mating holes in retainer.
(a) Aligning locating lugs on overdrive piston to
the two mating holes in retainer.
(b) Lubricate overdrive piston seals with Mopart
Door Ease, or equivalent.
(c) Install piston over Seal Guide 8114-3 and
inside Guide Ring 8114-1.
(d) Push overdrive piston into position in
retainer.(e) Verify that the locating lugs entered the lug
bores in the retainer.
PISTONS
DESCRIPTION
There are several sizes and types of pistons used in
an automatic transmission. Some pistons are used to
apply clutches, while others are used to apply bands.
They all have in common the fact that they are
round or circular in shape, located within a smooth
walled cylinder, which is closed at one end and con-
verts fluid pressure into mechanical movement. The
fluid pressure exerted on the piston is contained
within the system through the use of piston rings or
seals.
OPERATION
The principal which makes this operation possible
is known as Pascal's Law. Pascal's Law can be stated
as: ªPressure on a confined fluid is transmitted
equally in all directions and acts with equal force on
equal areas.º
Fig. 192 Installing/Aligning Case Gasket
1 - CASE GASKET
2 - BE SURE GOVERNOR TUBE FEED HOLES IN CASE AND
GASKET ARE ALIGNED
Fig. 193 Aligning Overdrive Piston Retainer
1 - PISTON RETAINER
2 - GASKET
3 - RETAINER BOLTS
21 - 418 AUTOMATIC TRANSMISSION - 48REDR
OVERRUNNING CLUTCH CAM/OVERDRIVE PISTON RETAINER (Continued)

Page 2258 of 2895

DODGE RAM 2003 Service Repair Manual PRESSURE
Pressure (Fig. 194) is nothing more than force
(lbs.) divided by area (in or ft.), or force per unit
area. Given a 100 lb. block and an area of 100 sq. in.
on the floor, the pressure exerted

PRESSURE
Pressure (Fig. 194) is nothing more than force
(lbs.) divided by area (in or ft.), or force per unit
area. Given a 100 lb. block and an area of 100 sq. in.
on the floor, the pressure exerted by the block is: 100
lbs. 100 in or 1 pound per square inch, or PSI as it is
commonly referred to.
PRESSURE ON A CONFINED FLUID
Pressure is exerted on a confined fluid (Fig. 195) 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 pressure. 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 down-
ward (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 pressure created equals 10 PSI.
Another interpretation of Pascal's Law is that regardless
of container shape or size, the pressure will be main-
tained throughout, as long as the fluid is confined. In
other words, the pressure in the fluid is the same every-
where within the container.
FORCE MULTIPLICATION
Using the 10 PSI example used in the illustration
(Fig. 196), 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. 196), 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. 194 Force and Pressure Relationship
Fig. 195 Pressure on a Confined Fluid
Fig. 196 Force Multiplication
DRAUTOMATIC TRANSMISSION - 48RE 21 - 419
PISTONS (Continued)

Page 2259 of 2895

DODGE RAM 2003 Service Repair Manual PISTON TRAVEL
The relationship between hydraulic lever and a
mechanical lever is the same. With a mechanical
lever its a weight-to-distance output rather than a
pressure-to-area output. Using the sam

Page 2260 of 2895

DODGE RAM 2003 Service Repair Manual DISASSEMBLY
(1) Remove planetary snap-ring from intermediate
shaft (Fig. 199). Discard snap-ring as it is not reus-
able.
(2) Remove front planetary gear and front annulus
gear as assembly (Fig. 200).

Page 2261 of 2895

DODGE RAM 2003 Service Repair Manual (5) Remove sun gear and driving shell as assembly
(Fig. 203).
(6) Remove tabbed thrust washer from rear plane-
tary gear (Fig. 204). Note washer position on gear for
assembly reference.
(7) Remove rea

(5) Remove sun gear and driving shell as assembly
(Fig. 203).
(6) Remove tabbed thrust washer from rear plane-
tary gear (Fig. 204). Note washer position on gear for
assembly reference.
(7) Remove rear planetary gear and rear annulus
gear from intermediate shaft (Fig. 205).
(8) Remove thrust washer from rear planetary
gear (Fig. 206).
INSPECTION
Inspect the planetary gear sets and annulus gears.
The planetary pinions, shafts, washers, and retaining
pins are serviceable. However, if a pinion carrier is
damaged, the entire planetary gear set must be
replaced as an assembly.
Replace the annulus gears if the teeth are chipped,
broken, or worn, or the gear is cracked. Replace theplanetary thrust plates and the tabbed thrust wash-
ers if cracked, scored or worn.
Inspect the machined surfaces of the intermediate
shaft. Be sure the oil passages are open and clear.
Replace the shaft if scored, pitted, or damaged.
Inspect the sun gear and driving shell. If either
component is worn or damaged, remove the sun gear
rear retaining ring and separate the sun gear and
thrust plate from the driving shell. Then replace the
necessary component.
Replace the sun gear as an assembly if the gear teeth
are chipped or worn. Also replace the gear as an assem-
bly if the bushings are scored or worn. The sun gear
bushings are not serviceable. Replace the thrust plate if
worn, or severely scored. Replace the driving shell if dis-
torted, cracked, or damaged in any way.
Replace all snap-rings during geartrain assembly.
Reusing snap-rings is not recommended.
Fig. 203 Sun Gear And Driving Shell Removal
1 - INTERMEDIATE SHAFT
2 - DRIVING SHELL
3 - SUN GEAR
Fig. 204 Rear Planetary Thrust Washer Removal
1 - SUN GEAR
2 - REAR PLANETARY THRUST WASHER
3 - DRIVING SHELL
Fig. 205 Rear Planetary And Annulus Gear Removal
1 - INTERMEDIATE SHAFT
2 - REAR ANNULUS GEAR
3 - REAR PLANETARY GEAR
Fig. 206 Rear Annulus Thrust Washer Removal
1 - REAR ANNULUS GEAR
2 - THRUST WASHER
21 - 422 AUTOMATIC TRANSMISSION - 48REDR
PLANETARY GEARTRAIN/OUTPUT SHAFT (Continued)

Page 2262 of 2895

DODGE RAM 2003 Service Repair Manual ASSEMBLY
(1) Lubricate sun gear and planetary gears with
transmission fluid during assembly. Use petroleum
jelly to lubricate intermediate shaft bushing surfaces,
thrust washers and thrust plates and

Page 2263 of 2895

DODGE RAM 2003 Service Repair Manual (6) Install tabbed thrust washer on front face of
rear planetary gear (Fig. 211). Seat washer tabs in
matching slots in face of gear carrier. Use extra
petroleum jelly to hold washer in place if desir

Page 2264 of 2895

DODGE RAM 2003 Service Repair Manual slots in face of gear carrier. Use extra petroleum jelly
to hold washer in place if desired.
(11) Install the torlon bushing onto the front plan-
etary carrier hub.
(12) Install front annulus gear ove

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