Professional™ Rear Upper Knuckle Bushing (45G31003) by ACDelco®. Quantity: 1 per Pack. Location: At Knuckle. ACDelco Professional Truck Bushings have a new dual-axis design adjuster for up to 25% greater range of adjustment over other styles of truck bushings. Technician-friendly inner sleeve design makes on-the-vehicle adjustments easy – a standard socket fits easily and securely over the inner hex for fast and accurate settings.