Slip (or axial length change) is almost required where universal joints are used to transmit power. Universal joints permit angular or offset misalignment while transmitting torque between power source and power user. Truck drive trains may use universal joints to connect any or all components between the engines, transmissions, auxiliary transmissions, transfer cases, axles, or axle wheels. Length variations during operation may be intentional for design function or unavoidable. These relative movements in trucks are generally allowed by a sliding section in the driveline. This paper will discuss prevalent conditions, current state-of-the-art, and what may be in the offing for the future.