Chevrolet Silverado / GMC Sierra. Service manual — part 1888

1. Remove the drive belt. Refer to Drive Belt Replacement - Accessory or Air

Conditioning Compressor Belt Replacement .

2. Move the drive belt tensioner through its full travel.

The movement should feel smooth.

There should be no binding.

The tensioner should return freely.

3. If any binding is observed, replace the drive belt tensioner. Refer to Drive Belt Tensioner

Replacement - Accessory or Drive Belt Tensioner Replacement - Air Conditioning .

4. Install the drive belt. Refer to of Air Conditioning Compressor Belt Replacement or

Drive Belt Replacement - Accessory .

DESCRIPTION AND OPERATION

CRANKCASE VENTILATION SYSTEM DESCRIPTION

A closed crankcase ventilation system is used in order to provide a more complete scavenging of
the crankcase vapors. Fresh air from the throttle body is supplied to the crankcase, mixed with
blow-by gases, and then passed through a crankcase ventilation valve into the intake manifold.

The primary control is through the crankcase ventilation valve which meters the flow at a rate
depending on manifold vacuum. To maintain idle quality, the crankcase ventilation valve restricts
the flow when intake manifold vacuum is high. If abnormal operating conditions arise, the system
is designed to allow excessive amounts of blow-by gases to back flow through the crankcase vent
tube into the engine air inlet to be consumed by normal combustion.

Filtered fresh air is routed from up-stream of the throttle blade to the front of the right rocker arm
cover via a formed rubber hose. To reduce the potential of oil pullover into the throttle bore area
due to back flow of the ventilation system, the fitting in the right rocker arm cover is shielded
from the rocker arms. From there fresh air and gases are routed through the crankcase and up to
the opposite rocker arm cover where the positive crankcase ventilation (PCV) valve is located.
Gases are then routed through a hose to the intake manifold.

DRIVE BELT SYSTEM DESCRIPTION

The drive belt system consists of the following components:

IMPORTANT: When the engine is operating the drive belt tensioner arm

will move. Do not replace the drive belt tensioner because of
movement in the drive belt tensioner arm.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

The drive belt

The drive belt tensioner

The drive belt idler pulley

The crankshaft balancer pulley

The accessory drive component mounting brackets

The accessory drive components

The power steering pump, if belt driven

The generator

The A/C compressor, if equipped

The engine cooling fan, if belt driven

The water pump, if belt driven

The vacuum pump, if equipped

The air compressor, if equipped

The drive belt system may use 1 belt or 2 belts. The drive belt is thin so that it can bend
backwards and has several ribs to match the grooves in the pulleys. The drive belts are made of
different types of rubbers, chloroprene or EPDM, and have different layers or plys containing
either fiber cloth or cords for reinforcement.

Both sides of the drive belt may be used to drive the different accessory drive components. When
the back side of the drive belt is used to drive a pulley, the pulley is smooth.

The drive belt is pulled by the crankshaft balancer pulley across the accessory drive component
pulleys. The spring loaded drive belt tensioner keeps constant tension on the drive belt to prevent
the drive belt from slipping. The drive belt tensioner arm will move when loads are applied to the
drive belt by the accessory drive components and the crankshaft.

The drive belt system may have an idler pulley, which is used to add wrap to the adjacent pulleys.
Some systems use an idler pulley in place of an accessory drive component when the vehicle is
not equipped with the accessory.

ENGINE COMPONENT DESCRIPTION

The 4.8, 5.3, 6.0, and 6.2 Liter V8 Engines

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 30: View Of Engine
Courtesy of GENERAL MOTORS CORP.

To assist in determining the applicable hardware and control system for each engine RPO, refer
to Engine Content Specifications.

Camshaft and Drive System - RPO LY2/LH6/LMG/LY5/LC9

A billet steel 1-piece camshaft is supported by 5 bearings pressed into the engine block. The
camshaft timing sprocket is mounted to the front of the camshaft and is driven by the crankshaft
sprocket through the camshaft timing chain. The camshaft position (CMP) sensor lobes are
incorporated into the front face of the camshaft sprocket with the CMP sensor mounted in the
engine front cover. A timing chain tensioner is mounted to the front of the engine block above the
crankshaft sprocket. The externally splined crankshaft sprocket is positioned to the crankshaft by

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

a key and keyway. The crankshaft sprocket external splines drive the oil pump drive gear. A
retaining plate mounted to the front of the engine block maintains camshaft location.

Camshaft and Drive System - RPO LY6/L76/L92

A billet steel 1-piece camshaft is supported by 5 bearings pressed into the engine block. The CMP
actuator is mounted to the front of the camshaft and retained by the CMP solenoid valve. The
CMP actuator is driven by the crankshaft sprocket through the camshaft timing chain. The CMP
sensor wheel is incorporated into the front face of the CMP actuator with the CMP sensor and
CMP actuator magnet mounted in the engine front cover. A timing chain tensioner is mounted to
the front of the engine block above the crankshaft sprocket. The externally splined crankshaft
sprocket is positioned to the crankshaft by a key and keyway. The crankshaft sprocket external
splines drive the oil pump drive gear. A retaining plate mounted to the front of the engine block
maintains camshaft location. Refer to Camshaft Position Actuator and Solenoid Valve
Description.

Crankshaft

The crankshaft is cast nodular iron. The crankshaft is supported by 5 crankshaft bearings. The
bearings are retained by crankshaft bearing caps which are machined with the engine block for
proper alignment and clearance. The crankshaft journals are undercut and rolled. The center main
journal is the thrust journal. A CKP reluctor ring is press-fit mounted at the rear of the crankshaft.
The reluctor ring is not serviceable separately.

Cylinder Heads

The cylinder heads are cast aluminum and have pressed in place powdered metal valve guides and
valve seats. Passages for the engine coolant air bleed system are at the front of each cylinder head.
The valve rocker arm covers are retained to the cylinder head by 4 center mounted rocker arm
cover bolts. RPO LY6, L76, and L92 use a high-flow cylinder head with an offset intake valve
rocker arm design.

Engine Block - RPO LH6/LC9/L76/L92

The engine block is a cam-in-block deep skirt 90 degree V-configuration with 5 crankshaft
bearing caps. The engine block is cast aluminum. The 5 crankshaft bearing caps each have 4
vertical M10 and 2 horizontal M8 mounting bolts. The camshaft is supported by 5 camshaft
bearings pressed into the block.

Engine Block - RPO LY2/LMG/LY5/LY6

The engine block is a cam-in-block deep skirt 90 degree V-configuration with 5 crankshaft

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.8L, 5.3L, 6.0L, 6.2L, or 7.0L - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado