Engine, A/T - Engine Compartment Rattle/Crackling Noise
Bulletin No.: 04-06-01-012ADate: January 05, 2007
TECHNICAL
Subject:
Rattle or Crackling Noise From Engine Compartment (Replace Flywheel)
Models:
2004 Chevrolet Silverado
2004 GMC Sierra
Built at Flint Assembly with Vortec(TM) 6.0L Engine (VIN U - RPO LQ4)
and Hydra-matic(R) Four Speed 4L80-E Automatic Transmission (RPO MT1)
Supercede:
This bulletin is being revised to inform dealerships that a flywheel spacer with longer bolts must be used when replacing the flywheel. Please discard Corporate Bulletin Number 04-06-01-012 (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment on a rattle or crackling noise coming from the engine compartment.
Cause
Misalignment of the flywheel to torque converter during assembly may have occurred on some vehicles built at Flint Assembly. If the pilot is not properly seated when the attachment bolts are torqued, the torque converter may not be correctly aligned, which may result in a bending fatigue failure to the flywheel. Some failures may be significant enough to cause a loss of driveability.
Correction
All 6.0L require a spacer and longer bolts for proper flywheel position.
Inspect the flywheel and replace if cracked or broken. If a cracked flywheel is observed, inspect the crankshaft thrust bearing for any signs of unusual wear and repair/replace as necessary. Refer to Engine Mechanical Section in SI.
The replacement flywheel has larger diameter bolt holes than the original flywheel. The flywheel does not use a locating pin for alignment, and will not initially seat against the crankshaft flange or spacer, but will be pulled onto the crankshaft by the engine flywheel bolts. Refer to Engine Flywheel Installation in SI for the required three stage tightening process.
Parts Information
Warranty Information
For vehicles repaired under warranty, use the table.
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