gearbox PEUGEOT BIPPER (AA_)

The crunching noise you’re experiencing going into third gear on your Peugeot Bipper (AA_) is a fairly common symptom of worn or damaged synchronizers (synchros) inside the gearbox. The third gear synchro tends to wear out first due to use, causing difficulty and crunching noises when shifting into that gear.

Besides worn synchros, other possible causes include:

- Worn selector bushes: These are rubber parts in the gearselector linkage that can wear out and cause the selector to be slightly misaligned, resulting in gear crunching. Replacing selector bushes is relatively inexpensive and doesn’t require gearbox removal.
- Clutch issues: If the clutch isn’t fully disengaging, you may hear crunching when engaging gears. Checking clutch adjustment and condition is useful.
- Low or incorrect gearbox oil: Using the wrong type of oil or old oil can cause poor synchro performance and grinding noises. Changing the gearbox oil to a high-quality synthetic oil like Mobil 1 or Castrol RS can help.
- Water ingress: Sometimes water contamination in the gearbox oil leads to corrosion and synchro wear.

If it only crunches occasionally and shifting otherwise works fine, the issue might still be manageable. However, persistent crunching means the synchro wear is worsening and the gearbox may eventually require either a synchro rebuild or full overhaul.

Common advice is to:
- Check and replace selector bushes first—this is often a fix without dropping the gearbox.
- Use the correct, high-quality gearbox oil and change it regularly.
- Adjust or service the clutch if needed.
- If problems persist, consider a gearbox rebuild focused on worn synchros.

This is a known issue for Peugeot Bipper and similar small Peugeot/Citroën vans, and many owners have found selector bush replacement combined with better gearbox oil greatly improved the crunching shifting into third gear.