The term CAR SHAFT is composed of two words, the first being 'CAR' and the second being 'SHAFT'. The crossword solution for this term is AXLE, which is a four-letter word. An AXLE is a central SHAFT for a rotating wheel or gear. In the context of a CAR, an AXLE is a SHAFT that connects the wheels to the transmission, allowing them to rotate together. It is an important part of the CAR's drivetrain, as it transmits power from the engine to the wheels.