Transmission
Gearbox (Manual & Automatic)
The gearbox changes the torque-speed ratio between the engine and the wheels.
Free guide
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Drivetrain flow
Interactive — tap a partTap a part to see how it fits in the system.
What it does
- Multiplies torque in low gears
- Allows the engine to stay in its power band
- Reverse gear and neutral
When it fails
- Whining or growling in a gear
- Difficulty selecting gears
- Clutch-like judder in autos
- Low or burnt transmission fluid
How to diagnose
- Check fluid level and smell
- Listen for noise per gear
- Test the clutch operation on manuals
- Read transmission codes on autos
Maintenance
- Change manual gearbox oil on schedule
- Automatics: follow the service interval
- Fix leaks early before damage
Use the diagnosis order. When a part fails, confirm each hypothesis with measurements before replacing anything — codes and symptoms overlap.