Repair of synchronizer of manual transmission (Opel Astra J)

If the gear engages unclearly or with great effort or does not engage at all, before disassembling the secondary shaft, check the operation of the synchronizer: the synchronizer clutch should move manually with little effort. If the clutch is difficult to move (does not move or moves only with great effort), repair the synchronizer or replace it as an assembly.

Spontaneous gear disengagement indicates wear or damage to the synchronizer clutch teeth and gear rings.

Synchronizers of I and II, as well as III and IV gears are identical in design, so they are repaired using the same techniques.

You will need a screwdriver.



1. Before disassembling, mark the position of the coupling relative to the hub.



2. Pry it off with a screwdriver..





3. …remove the two springs

Note: The second spring is not visible in the photo as it is located on the back side of the synchronizer.

4. Pry it off with a screwdriver..



5. …remove three crackers from the hub grooves…



6. …and remove the coupling from the hub.



7. Inspect the synchronizer parts. The springs should not have any signs of wear where they contact the crackers.

8. The crackers should not be deformed, and the locking protrusions of the crackers should not be significantly worn.



9. On the ends of the coupling splines…



10. …and the blocking rings should not have any chipping or creasing.



11. The hub should not have any nicks in the splines or signs of wear.





12. When installing the locking ring on the cone of the corresponding gear, the gap between the ends of the ring and gear rims must be at least 1 mm, otherwise replace the locking ring.

13. Assemble the synchronizer in the reverse order of disassembly, installing the coupling on the hub in accordance with the marks applied before disassembly.