A rag joint refers to the individual flexible joint found on automobiles and other machines. The rag joint is typically located on steering shafts that connect the steering wheel to the steering gear input shaft, usually at the steering gear end. They provide a small amount of flex for a steering shaft within a few degrees of the same plane as the steering gear input shaft. It also provides some damping of vibration coming from the steering system, providing some isolation for the steering wheel.
The rag joint consists of a piece of doughnut-shaped rubber with reinforcing cords vulcanized in it, similar to a tire. The rag joint is a disc which is bolted or riveted to flanges mounted on the ends of the shafts which connect the steering wheel shaft to the steering gear. The frayed cords are seen on the edge of this piece of rubber, hence the term "rag joint." The bolt holes themselves are often reinforced by steel tubes molded into the doughnut. An older vehicle with loose steering or "play in the steering wheel" is often found to have a worn out rag joint. One can then reach inside the cab and wiggle the steering wheel while watching the rag joint move without the input shaft moving. This extreme play condition may cause the vehicle to fail the vehicle inspection, and indicates that the worn part needs to be replaced.
KLM Performance stocks the Borgeson 000941 Replacement Rag Joint.