The contact owns a 2021 Chevrolet Silverado 1500. The contact stated that the vehicle was making an abnormal knocking sound while driving at various speeds and while idling. There was no warning light illuminated. The vehicle was taken to the dealer, where the engine lifters were replaced; however, the failure persisted. The vehicle was taken back to the dealer, where the contact was informed that the engine abnormal knocking sound was not sufficiently loud to issue a recall. The vehicle was not repaired. The contact related the failure to NHTSA Action Number: PE25001 (Engine, Engine and Engine Cooling). The manufacturer was not notified of the failure. The failure mileage was approximately 11,000.