Which of the following is a sign of a failing manual transmission?

The presence of grinding gears is a significant sign of a failing manual transmission. This occurs when the gears are not meshing properly, which can be caused by a variety of issues, including worn synchronizers, inadequate lubrication, or misalignment within the transmission. When shifting gears, the synchronizers are responsible for matching the speed of the gears, and if they are not functioning correctly, it can result in the gears grinding against each other rather than smoothly engaging. This not only indicates a potential failure but also can lead to further damage if not addressed promptly.

In contrast, quick gear changes, smooth acceleration, and consistent engagement are indicators of a well-functioning manual transmission. Quick gear changes often reflect driver skill and not necessarily a sign of transmission issues. Smooth acceleration means that the vehicle is effectively transmitting power to the wheels without hesitation or interruptions. Consistent engagement implies that the transmission is working correctly and the driver can shift gears without issue.