K 2500 Truck 4WD V8-454 7.4L VIN J SFI (1997)
Timing Chain: Service and Repair
Replacement
Camshaft Timing Chain and Sprocket Replacement
Removal Procedure
Tools Required
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J 28509-A Crankshaft Sprocket Remover
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J 41371 Reluctor Wheel Remover
1. Disconnect the negative battery cable.
Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF
before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in
contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its
components.
For Vehicles equipped with OnStar (UE1) with Back Up Battery:
The Back Up Battery is a redundant power supply to allow limited OnStar functionality in the event of a main vehicle battery power disruption to
the VCIM (OnStar module). Do not disconnect the main vehicle battery or remove the OnStar fuse with the ignition key in any position other than
OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the driver door should disable RAP) before
disconnecting power. Disconnecting power to the OnStar module in any way while the ignition is On or with RAP activated may cause activation
of the OnStar Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. Once the Back-Up Battery is
activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced.
2. Remove the air cleaner assembly.
3. Remove the engine cooling fan. Refer to Cooling System.
4. Remove the water pump. Refer to Cooling System.
5. Remove the engine front cover.
Important: If the crankshaft sensor reluctor ring is removed, a new crankshaft sensor reluctor ring must be installed.
6. Remove the reluctor ring from the crankcase using reluctor wheel remover.
7. Measure the camshaft timing chain free play. If the chain can be moved back and forth in, excess of 16 mm (0.625 inch), make a note that the
camshaft timing chain and the sprockets must be replaced during assembly.
