Main faults of a manual gearbox (Peugeot 406)

Extraneous noise in neutral gearbox position

• input shaft bearing is worn out (the noise is heard when the clutch pedal is released);
• the clutch release bearing is worn out.

Noise when only one gear is engaged

• the teeth of the gear of one gear are worn or damaged.

Difficulty shifting gears

• clutch damage;
• worn or damaged gear shift rods;
• the gear shift rods are not adjusted correctly;
• synchronizers are worn out.

Knocking out gears

• the gear shift rod is worn or damaged;
• the gear shift rods are not adjusted correctly;
• synchronizers are worn out;
• the gear shift forks are worn out.

Vibration

• low oil level;
• bearing wear.

Oil leaks

• wear of differential sealing rings;
• input shaft seal wear.

Source available on the website [PEUGEOTBOOK]