GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 1997 🢒 Sunfire 🢒 Transmission/Transaxle 🢒 Manual Transmission - M5 and MK7 🢒 Synchronizers

Synchronizers General Inspection


    Object Number: 4810 Size: SH
  1. Scribe a mark on the synchronizer hub and on the sleeve. This will help you to reinstall the parts in the same position.
  2. Clean all the synchronizer parts with appropriate solvent.
  3. Air dry all the synchronizer parts.
  4. Inspect the synchronizer parts for the following conditions:
    5. • Burrs
    • Cracks
    • Chamfer for excessive wear
    • Free movement of the clutching sleeves on their hubs
    • Worn or damaged clutch teeth
  5. The 1ST-2ND speed outer cone and the 3RD-4TH speed blocking ring are lined with friction material. The friction material cannot be checked visually for wear.
  6. Replace synchronizer parts that are worn or damaged.
  7. Replace a burred or nicked part that cannot be reconditioned by hand. Use a soft stone or crocus cloth.

    8. Object Number: 38587 Size: SH
  8. Inspect the brass 5TH speed gear blocking ring for wear and damage.

    9. Notice: Make certain the blocker rings are correctly identified before assembly. The 1st/2nd synchronizer blocker ring does not have friction material. The 3rd/4th synchronizer blocker ring has friction material. Assembling one blocker ring in place of the other will result in serious damage to the transmission.


    Object Number: 38721 Size: SH
  9. Assemble the 3RD speed gear blocking ring to the 3RD speed gear. Use a twisting motion in order to fully seat the parts.

    10. Object Number: 38591 Size: SH
  10. Measure the clearance between the blocker ring and inserts. Replace components if not within the following specifications listed below.
    11. 10.1. Use a feeler gauge.
    10.2. The nominal gap is 3.7 mm (0.146 inch) for new blocking rings.
    10.3. Measure the clearance between blocker ring and 3RD speed gear. Replace compoents if the gap is less than 0.8 mm (0.031 inch).

    Notice: Make certain the blocker rings are correctly identified before assembly. The 1st/2nd synchronizer blocker ring does not have friction material. The 3rd/4th synchronizer blocker ring has friction material. Assembling one blocker ring in place of the other will result in serious damage to the transmission.


    Object Number: 38720 Size: SH
  11. Assemble the 4TH speed gear blocking ring to the main drive gear. Use a twisting motion in order to fully seat the parts.

    12. Object Number: 38591 Size: SH
  12. Measure the clearance between the blocker ring and inserts. Replace components if not within the following specifications listed below.
    13. 12.1. Use a feeler gauge.
    12.2. The nominal gap is 3.7 mm 0.146 inch) for new blocking rings.
    12.3. Measure the clearance between blocker ring and 4TH speed gear. Replace compoents if the gap is less than 0.8 mm (0.031 inch).

    Notice: Make certain the blocker rings are correctly identified before assembly. The 1st/2nd synchronizer blocker ring does not have friction material. The 3rd/4th synchronizer blocker ring has friction material. Assembling one blocker ring in place of the other will result in serious damage to the transmission.


    Object Number: 38722 Size: SH
  13. Assemble the following parts using a twisting motion in order to fully seat them:
    14. 13.1. The needle bearing assembly to the 1ST speed gear
    13.2. The needle bearing sleeve
    13.3. The three-piece 1ST speed gear blocking ring assembly

    Object Number: 38591 Size: SH
  14. Measure the clearance between the blocker ring and inserts. Replace components if not within the following specifications listed below.
    15. 14.1. Use a feeler gauge.
    14.2. The nominal gap is 3.9 mm 0.154 inch) for new blocking rings.
    14.3. Measure the clearance between blocker ring and 1ST speed gear. Replace compoents if the gap is less than 0.8 mm (0.031 inch).

    Notice: Make certain the blocker rings are correctly identified before assembly. The 1st/2nd synchronizer blocker ring does not have friction material. The 3rd/4th synchronizer blocker ring has friction material. Assembling one blocker ring in place of the other will result in serious damage to the transmission.


    Object Number: 38723 Size: SH
  15. Assemble the following parts using a twisting motion in order to fully seat them:
    16. 15.1. The thrust washer to the 2ND speed gear
    15.2. The three-piece 2ND speed gear blocking ring assembly

    Object Number: 38591 Size: SH
  16. Measure the clearance between the blocker ring and inserts. Replace components if not within the following specifications listed below.
    17. 16.1. Use a feeler gauge.
    16.2. The nominal gap is 3.9 mm 0.154 inch) for new blocking rings.
    16.3. Measure the clearance between blocker ring and 2ND speed gear. Replace compoents if the gap is less than 0.8 mm (0.031 inch).

    Object Number: 38589 Size: SH
  17. Examine the fit between the hub and the sleeve of each synchronizer. An excessively tight or loose hub-to-sleeve fit will cause hard shifting.

    18. Object Number: 38592 Size: SH
  18. Examine the clutching teeth for evidence of gear clash.

    19. Object Number: 38594 Size: SH
  19. Examine the clutching teeth for gear hop-out.

Synchronizers Detent Springs Inspection

Detent Springs
  1. Inspect the springs for distortion, cracks or wear. Replace if these conditions are evident. Measure the spring length.
  2. Replace any spring not within specifications listed below.
    3. 2.1. Reverse detent spring greater than 65.6 mm (2.583 in.).
    2.2. All other detent springs greater than 26.2 mm (1.031 in.).