Terrestrial mobile robotics are increasingly important to a range of missions including planetary exploration, search and rescue, logistics, and national security. Many of these missions require the robot to operate on a broad variety of terrain. Wheels are ideal for energy efficiency but can suffer catastrophic failure when presented with obstacles or complex ground. Legs can help navigate obstacles but at the cost of energy efficiency. Physical adaptation can enable a robot to benefit from both modes of locomotion. This paper describes a new approach to physical adaptation through manipulation. Specifically, this paper examines how manipulators can be used to change the vehicle's mode of locomotion and improve energy efficiency and versatility. This paper presents “swappable propulsors”, which can be easily attached/detached to adapt the vehicle through the use of permanent magnets. A new robot system that uses its manipulator to discretely switch between wheeled and legged locomotion is created. The experimental results demonstrate how this approach provides a unique combination of energy efficiency and versatility. This work describes the design of swappable propulsors, analyzes how to manipulate them, and describes how they can be used to improve performance. This work extends on prior work with additional analysis, an improved robot prototype, and new experimental results.