An adjustment shim for the gear fork in the third gear of the Citroën 11CV is a precision component that ensures proper alignment and operation of the gearbox. This small yet essential part provides the necessary support and adjustment to minimize gear wear and promote smooth shifting. It is crucial for maintaining the performance and longevity of the transmission, especially in older models like the Citroën 11CV. Regular inspection and replacement are recommended to ensure optimal efficiency and prevent potential damage to the transmission.