1998 DODGE RAM 1500 Engine

CRANKSHAFT MAIN
BEARINGS
STANDARD PROCEDURE
MAIN BEARING FITTING
SELECT FIT IDENTIFICATION
The main bearings are ªselect fitº to achieve proper
oil clearances. For main bearing selection, the crank-
shaft position sensor target wheel has grade identifi-
cation marks stamped into it (Fig. 36). These marks
are read from left to right, corresponding with jour-
nal number 1, 2, 3, 4. The crankshaft position sensor
target wheel is mounted to the number 6 counter
weight on the crankshaft.
INSPECTION
Wipe the inserts clean and inspect for abnormal
wear patterns and for metal or other foreign material
imbedded in the lining. Normal main bearing insert
wear patterns are illustrated.
Inspect the back of the inserts for fractures, scrap-
ings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
MAIN BEARING JOURNAL DIAMETER
(CRANKSHAFT REMOVED)
Remove the crankshaft from the cylinder block(Re-
fer to 9 - ENGINE/ENGINE BLOCK/CRANKSHAFT
- REMOVAL).
Clean the oil off the main bearing journal.
Determine the maximum diameter of the journal
with a micrometer. Measure at two locations 90É
apart at each end of the journal.The maximum allowable taper is 0.008mm (0.0004
inch.) and maximum out of round is 0.005mm (0.002
inch). Compare the measured diameter with the jour-
nal diameter specification (Main Bearing Fitting
Chart). Select inserts required to obtain the specified
bearing-to-journal clearance.
Install the crankshaft into the cylinder block(Refer
to 9 - ENGINE/ENGINE BLOCK/CRANKSHAFT -
INSPECTION).
Check crankshaft end play.
Fig. 36 MARKINGS ON TARGET WHEEL
1 - REARMOST CRANKSHAFT COUNTER WEIGHT
2 - TARGET WHEEL
3 - MAIN BEARING SELECT FIT MARKINGS
9 - 44 ENGINE - 3.7LDR

CRANKSHAFT MAIN BEARING SELECTION
(1) Service main bearings are available in four
grades. The chart below identifies the four service
grades available.
Crankshaft
MarkingJOURNAL SIZE
SIZE mm (in.)
9R9Size 63.488 - 63.496 mm
(2.4995 - 2.4998 in.)
9S9Size 63.496 - 63.500 mm (2.4998 - 2.4999
in.)
9T9Size 63.500 - 63.504 mm (2.4999 - 2.501
in.)
9U9Size 63.504 - 63.512 mm (2.5001 - 2.5004
in.)
Bearing size
Bearing
CodeSize Application
Upper Bearing
A.2.443 - 2.447
mmUse with crankshaft
size9R9
(.0961 - .0963
in.)
B2.439 - 2.443
mmUse with crankshaft
9S, T9
(0.960 - .0961
in.)
C2.435 - 2.439
mmUse with crankshaft
9U9
(.0958 - .0960
in.)
Lower Bearing Main919and949
9192.441 - 2.447
mmUse with crankshaft
9R, S9
(.0961 -.0963
in.)
9292.435 - 2.441
mmUse with crankshaft
9T, U9
(.0958 - .0962
in.)
Crankshaft
MarkingJOURNAL SIZE
SIZE mm (in.)
Lower Main Bearing929and939
9392.429 - 2.435
mmUse with crankshaft
9R, S9
(.0956 - .0958
in.)
9492.423 - 2.429
mmUse with crankshaft
9T, U9
(.0953 - .0956
in.)
Bearing Clearances
Main91, 49
Crankshaft
9R9.004 - .034 mm ( .00015 - .0013 in.)
Crankshaft
9S9.004 - .030 mm ( .00015 - .0011 in.)
Crankshaft
9T9.006 - .032 mm (.0002 - .0012 in.)
Crankshaft
9U9.002 - .032 mm (.00007 -. 0012 in.)
Main92, 39
Crankshaft
9R9.016 - .046 mm (.0006 - .0018 in.)
Crankshaft
9S9.016 - .042 mm (.00062 - .016 in.)
Crankshaft
9T9.018 - .044 mm (.0007 - .0017 in.)
Crankshaft
9U9.014 - .044 mm (.0005 - .0017 in.)
DRENGINE - 3.7L 9 - 45
CRANKSHAFT MAIN BEARINGS (Continued)

CRANKSHAFT OIL SEAL - FRONT
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove accessory drive belt (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
REMOVAL).
(3) Remove A/C compressor mouning fasteners and
set aside.
(4) Drain cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(5) Remove upper radiator hose.
(6) Disconnect electrical connector for fan mounted
inside radiator shroud.
(7) Remove radiator shroud attaching fasteners.
NOTE: Transmission cooler line snaps into shroud
lower right hand corner.
(8)
Remove radiator cooling fan and shroud (Refer to
7 - COOLING/ENGINE/RADIATOR FAN - REMOVAL).
(9) Remove crankshaft damper bolt.
(10) Remove damper using Special Tools 8513
Insert and 1026 Three Jaw Puller (Fig. 37).
(11) Using Special Tool 8511, remove crankshaft
front seal (Fig. 38).
INSTALLATION
CAUTION: To prevent severe damage to the Crank-
shaft, Damper or Special Tool 8512, thoroughlyclean the damper bore and the crankshaft nose
before installing Damper.
(1) Using Special Tool 8348 and 8512, install
crankshaft front seal (Fig. 39).
(2) Install vibration damper (Refer to 9 - ENGINE/
ENGINE BLOCK/VIBRATION DAMPER - INSTAL-
LATION).
Fig. 37 Crankshaft Damper Removal
1 - SPECIAL TOOL 8513 INSERT
2 - SPECIAL TOOL 1026
Fig. 39 Crankshaft Front Seal Installation
1 - TIMING CHAIN COVER
2 - SPECIAL TOOL 8348
3 - SPECIAL TOOL 8512
Fig. 38 Crankshaft Front Seal Removal
1 - SPECIAL TOOL 8511
9 - 46 ENGINE - 3.7LDR

(3) Install radiator cooling fan and shroud (Refer
to 7 - COOLING/ENGINE/RADIATOR FAN -
INSTALLATION).
(4) Install upper radiator hose.
(5) Install A/C compressor and tighten fasteners to
54 N´m (40 ft. lbs.).
(6) Install accessory drive belt refer (Refer to 7 -
COOLING/ACCESSORY DRIVE/DRIVE BELTS -
INSTALLATION).
(7) Refill cooling system (Refer to 7 - COOLING -
STANDARD PROCEDURE).
(8) Connect negative cable to battery.
CRANKSHAFT OIL SEAL -
REAR
REMOVAL
NOTE: This procedure can be performed in vehicle.
(1) If being preformed in vehicle, remove the
transmission.
(2) Remove the flexplate (Refer to 9 - ENGINE/
ENGINE BLOCK/FLEX PLATE - REMOVAL).
NOTE: The crankshaft oil seal CAN NOT be reused
after removal.
NOTE: The crankshaft rear oil seal remover Special
Tool 8506 must be installed deeply into the seal.
Continue to tighten the removal tool into the seal
until the tool can not be turned farther. Failure to
install tool correctly the first time will cause tool to
pull free of seal without removing seal from engine.
(3) Using Special Tool 8506 (Fig. 40), remove the
crankshaft rear oil seal.
INSTALLATION
(1) Lubricate the crankshaft flange with engine oil.
(2) Position the magnetic seal guide Special Tool
8349-2 (Fig. 41) onto the crankshaft rear face. Then
position the crankshaft rear oil seal onto the guide.
Fig. 40 Crankshaft Rear Oil Seal Removal
1 - REAR CRANKSHAFT SEAL
2 - SPECIAL TOOL 8506
Fig. 41 Crankshaft Rear Oil Seal Guide Special Tool
8349-2 and Oil
1 - REAR CRANKSHAFT SEAL
2 - SPECIAL TOOL 8349-2 GUIDE
DRENGINE - 3.7L 9 - 47
CRANKSHAFT OIL SEAL - FRONT (Continued)

(3) Using Special Tools 8349 Crankshaft Rear Oil
Seal Installer and C-4171 Driver Handle (Fig. 42),
with a hammer, tap the seal into place. Continue to
tap on the driver handle until the seal installer seats
against the cylinder block crankshaft bore.
(4) Install the flexplate.
(5) Install the transmission.
FLEX PLATE
REMOVAL
(1) Remove the transmission.
(2) Remove the bolts and flexplate.
INSTALLATION
(1) Position the flexplate onto the crankshaft and
install the bolts hand tight.
(2) Tighten the flexplate retaining bolts to 95 N´m
(70 ft. lbs.) in the sequence shown (Fig. 43).
(3) Install the transmission.
PISTON & CONNECTING ROD
DESCRIPTION
CAUTION: Do not use a metal stamp to mark con-
necting rods as damage may result, instead use ink
or a scratch awl.The pistons are made of a high strength aluminum
alloy. The connecting rods are made of forged pow-
dered metal, with a ªfractured capº design. A full
floating piston pin is used to attach the piston to the
connecting rod (Fig. 44).
Fig. 42 Crankshaft Rear Oil Seal Installation
1 - REAR CRANKSHAFT SEAL
2 - SPECIAL TOOL 8349-1 INSTALLER
3 - SPECIAL TOOL C-4171 HANDLE
Fig. 43 Flexplate Tightening Sequence
1 - FLEXPLATE
Fig. 44 PISTON AND ROD ASSEMBLY
1 - CONNECTING ROD
2 - PISTON
3 - PISTON PIN
4 - OIL SLINGER SLOT
9 - 48 ENGINE - 3.7LDR
CRANKSHAFT OIL SEAL - REAR (Continued)

STANDARD PROCEDURE
CONNECTING ROD BEARING FITTING
Inspect the connecting rod bearings for scoring.
Check the bearings for normal wear patterns, scor-
ing, grooving, fatigue and pitting (Fig. 45). Replace
any bearing that shows abnormal wear.
Inspect the connecting rod journals for signs of
scoring, nicks and burrs (Fig. 46).
Misaligned or bent connecting rods can cause
abnormal wear on pistons, piston rings, cylinder
walls, connecting rod bearings and crankshaft con-
necting rod journals. If wear patterns or damage to
any of these components indicate the probability of a
misaligned connecting rod, inspect it for correct rod
alignment. Replace misaligned, bent or twisted con-
necting rods.
(1) Wipe the oil from the connecting rod journal.
(2) Lubricate the upper bearing insert and position
in connecting rod. Center bearing insert in connect-
ing rod (Fig. 47)
Fig. 45 Connecting Rod Bearing Inspection
1 - UPPER BEARING HALF
2 - MATING EDGES
3 - GROOVES CAUSED BY ROD BOLTS SCRATCHING JOURNAL
DURING INSTALLATION
4 - WEAR PATTERN - ALWAYS GREATER ON UPPER BEARING
Fig. 46 Scoring Caused by Insufficient Lubrication
or Damaged Crankshaft Journal
Fig. 47 Bearing Insert Location
1 - Connecting Rod
2 - Bearing Insert
- A, B less then .50 mm (.0196 in.)
DRENGINE - 3.7L 9 - 49
PISTON & CONNECTING ROD (Continued)

(3) Use piston ring compressor and Guide Pins
Special Tool 8507 (Fig. 48) to install the rod and pis-
ton assemblies. The oil slinger slots in the rods must
face front of the engine. The ªFº's near the piston
wrist pin bore should point to the front of the engine.
(4) Install the lower bearing insert in the bearing
cap. Center bearing insert in connecting rod (Fig. 47).
The lower insert must be dry. Place strip of Plasti-
gage across full width of the lower insert at the cen-
ter of bearing cap. Plastigage must not crumble in
use. If brittle, obtain fresh stock.
(5) Install bearing cap and connecting rod on the
journal and tighten bolts to 27 N´m (20 ft. lbs.) plus a
90É turn. DO NOT rotate crankshaft. Plastigage will
smear, resulting in inaccurate indication.
(6) Remove the bearing cap and determine amount
of bearing-to-journal clearance by measuring the
width of compressed Plastigage (Fig. 49). Refer to
Engine Specifications for the proper clearance.Plas-
tigage should indicate the same clearance
across the entire width of the insert. If the
clearance varies, it may be caused by either atapered journal, bent connecting rod or foreign
material trapped between the insert and cap or
rod.
(7) If the correct clearance is indicated, replace-
ment of the bearing inserts is not necessary. Remove
the Plastigage from crankshaft journal and bearing
insert. Proceed with installation.
(8) If bearing-to-journal clearance exceeds the
specification, determin which services bearing set to
use the bearing sizes are as follows:
Bearing
MarkSIZE USED WITH
JOURNAL SIZE
.025 US.025 mm 57.883-57.867 mm
(.001 in.) (2.2788-2.2783 in.)
Std.STANDARD 57.908-57.892 mm
(2.2798-2.2792 in.)
.250 US.250 mm 57.658-57.646 mm
(.010 in.) (2.2700-2.2695 in.)
CAUTION: Connecting Rod Bolts are Torque to
Yield Bolts and Must Not Be Reused. Always
replace the Rod Bolts whenever they are loosened
or removed.
(9) Repeat the Plastigage measurement to verify
your bearing selection prior to final assembly.
Fig. 48 Piston and Connecting Rod -Installation -
Typical
1 - ªFº TOWARD FRONT OF ENGINE
2 - OIL SLINGER SLOT
3 - RING COMPRESSOR
4 - SPECIAL TOOL 8507
Fig. 49 Measuring Bearing Clearance with
Plastigage
1 - PLASTIGAGE SCALE
2 - COMPRESSED PLASTIGAGE
9 - 50 ENGINE - 3.7LDR
PISTON & CONNECTING ROD (Continued)

(10) Once you have selected the proper insert,
install the insert and cap. Tighten the connecting rod
bolts to 27 N´m (20 ft. lbs.) plus a 90É turn.
Slide snug-fitting feeler gauge between the con-
necting rod and crankshaft journal flange (Fig. 50).
Refer to Engine Specifications for the proper clear-
ance. Replace the connecting rod if the side clearance
is not within specification.
STANDARD PROCEDURE - PISTON FITTING
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, capable of reading in 0.003 mm (
.0001 in.) INCREMENTS is required. If a bore gauge
is not available, do not use an inside micrometer.
(2) Measure the inside diameter of the cylinder
bore at a point 38.0 mm (1.5 inches) below top of
bore. Start perpendicular (across or at 90 degrees) to
the axis of the crankshaft at point A and then take
an additional bore reading 90 degrees to that at point
B (Fig. 52).
(3) The coated pistons will be serviced with the
piston pin and connecting rod pre-assembled.
(4) The coating material is applied to the piston
after the final piston machining process. Measuring
the outside diameter of a coated piston will not pro-
vide accurate results (Fig. 51). Therefore measuring
the inside diameter of the cylinder bore with a dial
Bore Gauge isMANDATORY. To correctly select the
proper size piston, a cylinder bore gauge capable of
reading in 0.003 mm (.0001 in.) increments is
required.
(5) Piston installation into the cylinder bore
requires slightly more pressure than that required
for non-coated pistons. The bonded coating on the
piston will give the appearance of a line-to-line fit
with the cylinder bore.
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the following components:
²Oil pan and gasket/windage tray (Refer to 9 -
ENGINE/LUBRICATION/OIL PAN - REMOVAL).
²Cylinder head covers (Refer to 9 - ENGINE/
CYLINDER HEAD/CYLINDER HEAD COVER(S) -
REMOVAL) and (Refer to 9 - ENGINE/CYLINDER
HEAD/CYLINDER HEAD COVER(S) - REMOVAL).
Fig. 50 Checking Connecting Rod Side Clearance -
Typical
Fig. 51 DO NOT MEASURE MOLY COATED PISTON
1 - MOLY COATED
2 - MOLY COATED
Fig. 52 BORE GAUGE - TYPICAL
1 - FRONT
2 - BORE GAUGE
3 - CYLINDER BORE
4 - 38 MM (1.5 in)
DRENGINE - 3.7L 9 - 51
PISTON & CONNECTING ROD (Continued)