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Synchronizers Cleaning and Inspection

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
    Fig 1: View Of Stepped Effect On The Synchronizers Teeth
    GM648209Courtesy of GENERAL MOTORS CORP.
    IMPORTANT: When you service the synchronizers, retain them in the order that they are removed. Mark the parts to ensure the correct position for inspection and assembly.
  1. Clean all the synchronizer parts in a suitable cleaning solvent and air dry all the parts.
  2. Inspect the 1st/2nd gear and the 3rd/4th gear synchronizer hubs for a force fit on the output shaft.
  3. Replace synchronizer hubs that do not require a force fit.
  4. Inspect the synchronizer hub for wear on the external splines. A stepped effect on the teeth, due to wear, may cause shift concerns.
  5. Replace a worn hub.
  6. Correct the cause, such as, but not limited to the following conditions:
    • Engine related vibrations
    • Driving at a low speed in a high gear
    • Defective vibration damper or crankshaft
    7. Fig 2: Identifying Damage On Synchronizer Sleeve Teeth
    GM1238251Courtesy of GENERAL MOTORS CORP.
  7. Inspect the synchronizer sleeve teeth (a) for the following conditions, which may cause shift concerns:
    • Grated teeth
    • Chipped off teeth
    • Blunted teeth
  8. Inspect the synchronizer sleeve detent stops (b) for wear or for being chipped off.
  9. Replace the synchronizer assembly if the teeth or stops show the above conditions.
    10. Fig 3: View Of Synchronizer Blocker Rings Grooves
    GM1368674Courtesy of GENERAL MOTORS CORP.
  10. Inspect the synchronizer blocker rings for worn away grooves (a).
  11. Replace the blocker ring assembly if the blocker ring grooves are worn.
    12. Fig 4: Inspecting Synchronizer Blocker Rings For Wear Or Damage
    GM648208Courtesy of GENERAL MOTORS CORP.
  12. Inspect the synchronizer blocker rings for worn shift teeth.
  13. Inspect the internal ring for being warped or damaged.
  14. Inspect the outer ring for worn grooves.
  15. Replace the synchronizer assembly for any of the above conditions.
    16. Fig 5: Ensuring Blocking Ring Locks
    GM881125Courtesy of GENERAL MOTORS CORP.
  16. Install the synchronizer blocking rings to the correct speed gear.
  17. Inspect the braking effect of the blocking ring. Turn the blocking ring in one direction while pushing to the gear cone. Ensure the ring locks.
  18. If the ring does not lock, replace the synchronizer assembly.
    19. Fig 6: Measuring Blocker Ring To Gear Clearance
    GM648192Courtesy of GENERAL MOTORS CORP.
  19. Except for 5th gear, measure the blocker ring to gear clearance.
    1. Assemble the correct blocker ring to the correct gear.
    2. Apply pressure to the blocker ring to fully seat the ring.
    3. Using a feeler gage, measure between the blocker ring teeth and the teeth on the gear.

      Specification: 

      • Minimum Clearance 4th Gear: 0.8 mm (0.031 in)
      • Minimum Clearance 3rd Gear: 0.8 mm (0.031 in)
      • Minimum Clearance 2nd Gear: 0.8 mm (0.031 in)
      • Minimum Clearance 1st Gear: 0.8 mm (0.031 in)

  20. If using a NEW blocker ring and the standard clearance can not be obtained, replace the gear.
    21. Fig 7: View Of Pressure Pieces & Springs
    GM1504132Courtesy of GENERAL MOTORS CORP.
  21. Inspect the pressure pieces for wear or damage.
  22. Inspect the springs for distortion.
  23. Replace the worn pressure pieces or faulty springs.
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