The contact owns a 2021 GMC Yukon XL. The contact stated while her husband was driving at an undisclosed speed, the engine made an abnormal loud sound, and the vehicle became undrivable. The vehicle was taken to Midas, where an unknown repair was performed. Additionally, the contact stated while driving 50-55 MPH on the expressway, the vehicle shuddered significantly, and the engine made an abnormal loud knocking sound. Unknown warning lights were illuminated. The contact was able to exit the expressway and drove back to Midas, where the contact was informed that the engine needed to be replaced, and the mechanic provided an estimated fee for the repair. The vehicle was towed to the dealer, where it was diagnosed that the engine needed to be replaced; however, the part was not available. The vehicle remained at the dealer for approximately three months. The vehicle was not repaired. The contact related the failure to NHTSA Action Number: PE25001(Engine, Engine and Engine and Cooling). The manufacturer was notified of the failure and informed that the part was not available. The failure mileage was approximately 73,000.