Transmission
Gearbox
Matches engine torque to speed through different ratios (geared bikes).
How it works
The gearbox contains gear pairs engaged by shift forks operated through the gear selector. Each ratio strikes a different balance between torque and speed. A clutch that doesn't disengage cleanly, or worn-out oil, makes shifting notchy; worn shift forks or gear dogs can cause gears to jump out under load - a serious repair requiring the engine to be opened up.
Maintenance tips
- Most shifting problems actually come from the clutch or the oil, not the gearbox itself.
- Gears that jump out on their own call for a professional diagnosis.
Related symptoms
⚠️ The information on this page is provided for educational purposes to help you understand the role and operation of the part. It replaces neither a physical inspection nor the judgment of a certified mechanic. Before any work on a safety-critical component (braking, steering, transmission, suspension), have the part's condition confirmed by a professional.