Dodge Ram Truck 1500-2500-3500. Manual — part 1305
The exhaust manifolds (1,2) are log style with a pat-
ented flow enhancing design to maximize perfor-
mance. The exhaust manifolds are made of high
silicon molybdenum cast iron. A perforated core graph-
ite exhaust manifold gasket is used to improve sealing
to the cylinder head. The exhaust manifolds are cov-
ered by a three layer laminated heat shield (3) for
thermal protection and noise reduction. The heat
shields are fastened with a torque prevailing nut that
is backed off slightly to allow for the thermal expan-
sion of the exhaust manifold.
REMOVAL
RIGHT EXHAUST MANIFOLD
1. Disconnect the negative cable from the battery.
2. Raise and support the vehicle.
3. Remove the bolts and nuts attaching the exhaust
pipe to the engine exhaust manifold.
4. Lower the vehicle.
5. Remove the exhaust heat shield (1).
6. Remove bolts, nuts and washers attaching mani-
fold to cylinder head.
7. Remove manifold and gasket from the cylinder
head.
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ENGINE - 3.7L - SERVICE INFORMATION
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LEFT EXHAUST MANIFOLD
1. Disconnect the negative cable from the battery.
2. Raise and support the vehicle.
3. Remove the bolts and nuts attaching the exhaust
pipe to the engine exhaust manifold.
4. Lower the vehicle.
5. Remove the exhaust heat shields (1).
6. Remove bolts, nuts and washers attaching mani-
fold to cylinder head.
7. Remove manifold and gasket from the cylinder
head.
INSTALLATION
RIGHT EXHAUST MANIFOLD
CAUTION: If the studs came out with the nuts when removing the engine exhaust manifold, install new
studs. Apply sealer on the coarse thread ends. Water leaks may develop at the studs if this precaution is
not taken.
1. Position the engine exhaust manifold and gasket on the two studs located on the cylinder head. Install conical
washers and nuts on these studs.
2. Install remaining conical washers. Starting at the center arm and working outward, tighten the bolts and nuts to
25 N·m (18 ft. lbs.) torque.
3. Install the exhaust heat shields.
4. Raise and support the vehicle.
CAUTION: Over tightening heat shield fasteners, may cause shield to distort and/or crack.
5. Assemble exhaust pipe to manifold and secure with bolts, nuts and retainers. Tighten the bolts and nuts to 34
N·m (25 ft. lbs.) torque.
LEFT EXHAUST MANIFOLD
CAUTION: If the studs came out with the nuts when removing the engine exhaust manifold, install new
studs. Apply sealer on the coarse thread ends. Water leaks may develop at the studs if this precaution is
not taken.
1. Position the engine exhaust manifold and gasket on the two studs located on the cylinder head. Install conical
washers and nuts on these studs.
2. Install remaining conical washers. Starting at the center arm and working outward, tighten the bolts and nuts to
25 N·m (18 ft. lbs.) torque.
3. Install the exhaust heat shields.
4. Raise and support the vehicle.
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ENGINE - 3.7L - SERVICE INFORMATION
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CAUTION: Over tightening heat shield fasteners, may cause shield to distort and/or crack.
5. Assemble exhaust pipe to manifold and secure with bolts, nuts and retainers. Tighten the bolts and nuts to 34
N·m (25 ft. lbs.) torque.
VALVE TIMING
DESCRIPTION
The timing drive system has been designed to provide quiet performance and reliability to support a non-free
wheeling engine. Specifically the intake valves are non-free wheeling and can be easily damaged with forceful
engine rotation if camshaft-to-crankshaft timing is incorrect. The timing drive system consists of a primary chain (6),
two secondary timing chain drives (1,4) and a counterbalance shaft drive.
OPERATION
The primary timing chain is a single inverted tooth chain type. The primary chain drives the large 50 tooth idler
sprocket directly from a 25 tooth crankshaft sprocket. Primary chain motion is controlled by a pivoting leaf spring
tensioner arm and a fixed guide. The arm and the guide both use nylon plastic wear faces for low friction and long
wear. The primary chain receives oil splash lubrication from the secondary chain drive and designed oil pump leak-
age. The idler sprocket assembly connects the primary chain drive, secondary chain drives, and the counterbalance
shaft. The idler sprocket assembly consists of two integral 26 tooth sprockets a 50 tooth sprocket and a helical gear
that is press-fit to the assembly. The spline joint for the 50 tooth sprocket is a non serviceable press fit anti rattle
type. A spiral ring is installed on the outboard side of the 50 tooth sprocket to prevent spline disengagement. The
idler sprocket assembly spins on a stationary idler shaft. The idler shaft is a light press-fit into the cylinder block. A
large washer on the idler shaft bolt and the rear flange of the idler shaft are used to control sprocket thrust move-
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ENGINE - 3.7L - SERVICE INFORMATION
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ment. Pressurized oil is routed through the center of the idler shaft to provide lubrication for the two bushings used
in the idler sprocket assembly.
There are two secondary drive chains, both are roller type, one to drive the camshaft in each SOHC cylinder head.
There are no shaft speed changes in the secondary chain drive system. Each secondary chain drives a 26 tooth
cam sprocket directly from the 26 tooth sprocket on the idler sprocket assembly. A fixed chain guide and a hydraulic
oil damped tensioner are used to maintain tension in each secondary chain system. The hydraulic tensioners for the
secondary chain systems are fed pressurized oil from oil reservoir pockets in the block. Each tensioner incorporates
a controlled leak path through a device known as a vent disc located in the nose of the piston to manage chain
loads. Each tensioner also has a mechanical ratchet system that limits chain slack if the tensioner piston bleeds
down after engine shut down. The tensioner arms and guides also utilize nylon wear faces for low friction and long
wear. The secondary timing chains receive lubrication from a small orifice in the tensioners. This orifice is protected
from clogging by a fine mesh screen which is located on the back of the hydraulic tensioners.
STANDARD PROCEDURE
MEASURING TIMING CHAIN WEAR
NOTE: This procedure must be performed with the
timing chain cover removed.
1. Remove the timing chain cover (Refer to 9 -
ENGINE/VALVE
TIMING/TIMING
BELT/CHAIN
AND SPROCKETS - REMOVAL).
2. To determine if the secondary timing chains are
worn, rotate the engine clockwise until maximum
tensioner piston (2) extension is obtained. Measure
the distance between the secondary timing chain
tensioner housing and the step ledge on the piston.
The measurement at point (A) must be less than
15mm (.5906 inches).
3. If the measurement exceeds the specification the
secondary timing chains are worn and require
replacement (Refer to 9 - ENGINE/VALVE TIMING/
TIMING
BELT/CHAIN
AND
SPROCKETS
-
REMOVAL).
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ENGINE - 3.7L - SERVICE INFORMATION
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