GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Generic 🢒 1999 🢒 Unit Repair 🢒 Transmission/Transaxle 🢒 Manual Transmission - MM6 (Y Car) 🢒 Shimming Procedures

Input Shaft, Mainshaft, and Countershaft

Tools Required

    • J 8001 Dial Indicator Set
    • J 39444-1 Countershaft End Play Rod
  1. Rotate the transmission adapter plate to the vertical position.

    2. Object Number: 105694 Size: SH
  2. Install the following assemblies in order:
    3. 2.1. The input shaft to the adapter plate
    2.2. Align the 4th speed gear blocking ring to the input shaft.
    2.3. The mainshaft assembly
    2.4. The countershaft (lift up the mainshaft enough to install the countershaft.)

    Object Number: 38424 Size: SH
  3. Install the transmission case.

    4. Object Number: 105692 Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  4. Install the adapter plate to transmission case bolts.

    5. Tighten
    Tighten the bolts to 35 N·m (26 Ib ft).


    Object Number: 38633 Size: SH
  5. Measure the input shaft/mainshaft end play using the following procedure:
    6. 5.1. Place the tip of the J 8001 -3 on the end of the mainshaft.
    5.2. Move the input shaft up and down.
    5.3. Record the measurement.
  6. Select a shim to achieve 0.00-0.05 mm (0.000-0.002 in) preload.
  7. Remove the J 8001 -3.

    8. Object Number: 105695 Size: SH
  8. Remove the adapter plate plug.

    9. Object Number: 38630 Size: SH
  9. Place the tip of the J 8001 -3 on the end of the countershaft.
  10. Measure the countershaft end play using the following procedure:
    11. 10.1. Install the J 39444-1 through the adapter plate plug hole. Screw the J 39444-1 into the countershaft.
    10.2. Move the countershaft up and down with the countershaft end play rod J 39444-1 .
    10.3. Record the measurement.
  11. Select a shim to achieve 0.00-0.05 mm (0.000-0.002 in) preload.
  12. Remove the J 8001 -3.
  13. Remove the J 39444-1 .

    14. Object Number: 105692 Size: SH
  14. Remove the adapter plate to the transmission case bolts.

    15. Object Number: 38424 Size: SH
  15. Remove the transmission case.

    16. Object Number: 105694 Size: SH
  16. Remove the following parts in order:
    17. 16.1. The countershaft (lift up the mainshaft enough to remove the countershaft).
    16.2. The mainshaft assembly
    16.3. The input shaft from the adapter plate
    16.4. The input shaft bearing race
    16.5. The countershaft bearing race

Countershaft Extension

Tools Required

    • J 8001 Dial Indicator Set
    • J 39444-2 Countershaft Extension End Play Rod

    Object Number: 38631 Size: SH

    Important: The following procedure cannot be performed accurately until the countershaft shimming procedure has been completed and the transmission has been assembled to the point of installing the countershaft extension.

  1. Rotate the transmission in the horizontal position.
  2. Install the countershaft extension to the countershaft. Make sure the splines fully engage.

    3. Object Number: 74203 Size: SH

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  3. Install the extension housing and the extension housing retainer bolts.

    4. Tighten
    Tighten the bolts to 35 N·m (26 Ib ft).


    Object Number: 105695 Size: SH
  4. Remove the plug from the adapter plate.

    5. Object Number: 350593 Size: SH
  5. Install the J 39444-2 through the adapter plate plug hole.
  6. Screw J 39444-2 into the countershaft extension.

    7. Object Number: 38428 Size: SH
  7. Measure the countershaft extension end play using the following procedure:
    8. 7.1. Install a J 8001 so the tip is on the end of the countershaft extension end play rod.
    7.2. Rotate the transmission in the vertical position.
    7.3. Move the countershaft extension up and down using the J 39444-2 .
    7.4. Record the measurement.
  8. Select a shim to achieve 0.05-0.13 mm (0.002-0.005 in) axial play.
  9. Remove the J 8001 .
  10. Remove the J 39444-2 .

    11. Object Number: 38436 Size: SH
  11. Apply sealant GM P/N United States 12346004, GM P/N Canada 10953480 or the equivalent to the plug threads.

    12. Object Number: 105695 Size: SH
  12. Install the adapter plate plug.

    13. Tighten
    Tighten the plug to 27 N·m (20 Ib ft).


    Object Number: 38631 Size: SH
  13. Install the countershaft extension.
  14. Install the countershaft extension bearing race.

    15. Object Number: 74203 Size: SH
  15. Install the extension housing bolts and the extension housing.