A high-pitched whistling or squeal sound may be heard at idle on some 2022-2023 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD models equipped with the 6.6L V8 gasoline engine (RPO L8T). The sound may be most noticeable at the rear main seal of the engine and may continue for several seconds after the engine is turned off.
The whistling sound may be caused by excessive crankcase vacuum from a restriction at the Positive Crankcase Ventilation (PCV) tube of the air cleaner outlet duct. (Fig. 13)
Fig. 13
Remove the oil cap or oil level indicator and verify if the sound is eliminated. If the sound is no longer heard, check for a restriction at the PCV tube. (Fig. 14, #2)
Fig. 14
Replace the air cleaner outlet duct if a restriction is found. Refer to Air Cleaner Outlet Duct Replacement in the appropriate Service Information.
Check Bulletin #23-NA-017 for more information, including part numbers.
– Thanks to Bryan Salisbury
