What is the main cause of damage to a manual gearbox?

The main cause of damage to a manual gearbox is changing gear without using the clutch. The clutch in a manual transmission is crucial for smoothly engaging and disengaging the engine from the drivetrain. When a driver shifts gears without utilizing the clutch, it places excessive stress on the gearbox components, particularly the synchronizers and gears themselves. This can lead to grinding of the gears, difficulty in shifting, and ultimately, significant internal wear or damage to the gearbox.

Using the clutch properly allows for a smooth transition between gears, reducing wear on the components and maintaining the integrity of the gearbox. It helps in aligning the gears properly during the shifting process, preventing metal-on-metal contact that occurs when shifting without the clutch. Over time, improper shifting can lead to costly repairs or the need for a complete gearbox replacement.