WHILE DRIVING IN TOWN ON HWY 20, THE FRONT RIGHT WHEEL ASSEMBLY SEPARATED FROM THE AXLE. THE VEHICLE PULLED TO THE RIGHT CAUSING ME TO COLLIDE WITH A BOULDER IN THE SIDE OF THE HILL. HITTING THE BOULDER DEPLOYED BOTH AIRBAGS, PUT THE TRUCK UP ON IT'S TWO LEFT TIRES AND SENT THE VEHICLE BACK INTO THE HIGHWAY. WHEN THE TRUCK CAME TO A STOP I GOT OUT OF THE TRUCK TO FIND THE RIGHT FRONT TIRE/RIM/BRAKE ASSEMBLY RESTING AGAINST THE CURB APPROXIMATELY 15 FEET BEHIND THE VEHICLE.