Some Chevrolet Camaro owners report experiencing a loud rumbling noise from the trunk area even after axle tightening. This issue may be attributed to worn brake pads, which can produce grinding or squealing noises when backing up. Additionally, some owners find that an exhaust leak can lead to unusual sounds emanating from the trunk. Other potential sources of the rumbling noise include transmission or driveshaft issues, which can be difficult to diagnose without specialized tools. Worn or damaged wheel bearings may also contribute to the rumbling sounds transmitted through the vehicle's body. Given these concerns, it is advisable for owners to seek a thorough inspection by a qualified mechanic to identify and address the underlying problem effectively.