While driving on a straight roadway the right rear wheel hub broke off of the rear axle. This caused the truck to turn to the left out of control. The truck crossed over the center line while the entire wheel/tire separated from the wheel well of the truck. The wheel/tire traveled another 50 yards off the roadway into a field. The truck struck a hill on the other side of the road deploying the side airbags due to impact with a road sign. The wheel hub/axle was inspected by a mechanic and the insurance company. The wheel hub was determined to be a defective part by the mechanic and insurance company. The wheel hub had noticeable rust where the axle was connected to the wheel hub. The truck was totaled and removed by the insurance company.