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Home › Subaru › 2021 › WRX STI › Repair and Diagnosis › Transmission › Manual Trans › Manual Transaxle & Differential (TY856) › Main Shaft Assembly › Assembly

Main Shaft Assembly: Assembly

NOTE: When replacing the following parts, replace as a set.
  • Coupling sleeve and synchronizer hub
  • 3rd outer baulk ring, 3rd synchro cone and 3rd inner baulk ring
  • Double taper roller bearing
  1. Apply adequate transmission gear oil to the main shaft, 3rd needle bearing and 3rd drive gear inner surface.
  2. Install the 3rd needle bearing and 3rd drive gear to the main shaft.
    G13648114Courtesy of SUBARU OF AMERICA, INC.
  3. Install the 3rd inner baulk ring, 3rd synchro cone and 3rd outer baulk ring.
    G13648115Courtesy of SUBARU OF AMERICA, INC.
    NOTE: Install the 3rd synchro cone by aligning the protrusion of the 3rd synchro cone with the hole on the 3rd drive gear.
    G05336142Courtesy of SUBARU OF AMERICA, INC.
  4. Install the 3rd-4th synchronizer hub and 4th needle bearing race.
    CAUTION: Apply transmission gear oil onto sliding or revolving surfaces before installation.
    1. Being careful of the install direction of the 3rd-4th synchronizer hub, set to the main shaft.
      G13648117Courtesy of SUBARU OF AMERICA, INC.
    2. With the main shaft oil hole and 4th needle bearing race oil hole out of alignment, attach to the main shaft.
      G06338363Courtesy of SUBARU OF AMERICA, INC.
    3. Using the ST, push in to the 3rd-4th synchronizer hub and 4th needle bearing race all at once.

      ST1 18651AA000 INSTALLER 

      ST2 398177700 INSTALLER 

      CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
      NOTE: When pushing into the 3rd-4th synchronizer hub and 4th needle bearing race, move the 3rd outer baulk ring to match the protrusion of the 3rd outer baulk ring and the cut out of the 3rd-4th synchronizer hub.
      G13648119Courtesy of SUBARU OF AMERICA, INC.
  5. Make sure that the 3rd drive gear can be turned smoothly by hand. If it does not turn smoothly, reassemble.
  6. Attach the 3rd-4th shifting insert at the appropriate position of the 3rd-4th coupling sleeve.
    NOTE:
    • The location angle of each shifting insert is 120°.
    • Refer to the following figure to install the shifting insert.
    G06346025Courtesy of SUBARU OF AMERICA, INC.
  7. Attach the 3rd-4th coupling sleeve to the 3rd-4th synchronizer hub.
    CAUTION: Apply transmission gear oil onto sliding or revolving surfaces before installation.
    NOTE:
    • There is an identification groove on the 3rd-4th coupling sleeve.
    • Place the groove towards the 3rd drive gear, and attach the 3rd-4th coupling sleeve.
    G13648121Courtesy of SUBARU OF AMERICA, INC.
  8. Install the 4th baulk ring.
    G05003392Courtesy of SUBARU OF AMERICA, INC.
  9. Apply adequate transmission gear oil to the main shaft, 4th needle bearing and 4th drive gear inner surface.
  10. Install the 4th needle bearing and 4th drive gear.
    G13648123Courtesy of SUBARU OF AMERICA, INC.
  11. Install the 5th drive gear bushing.
    1. With the main shaft oil hole and 5th drive gear bushing oil hole out of alignment, attach to the main shaft.
      G13648124Courtesy of SUBARU OF AMERICA, INC.
    2. Using the ST, push into the 5th drive gear bushing.

      ST1 18651AA000 INSTALLER 

      ST2 398177700 INSTALLER 

      CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
      G05003395Courtesy of SUBARU OF AMERICA, INC.
  12. Make sure that the 4th drive gear can be turned smoothly by hand. If it does not turn smoothly, reassemble.
  13. Apply adequate transmission gear oil to the main shaft, 5th needle bearing and 5th drive gear inner surface.
  14. Install the 5th needle bearing and 5th drive gear.
    G13648126Courtesy of SUBARU OF AMERICA, INC.
  15. Install the 5th baulk ring.
    G05003397Courtesy of SUBARU OF AMERICA, INC.
  16. Install the 5th-6th synchronizer hub.
    CAUTION: Apply transmission gear oil onto sliding or revolving surfaces before installation.
    1. Being careful of the install direction of the 5th-6th synchronizer hub, set to the main shaft.
      G13648128Courtesy of SUBARU OF AMERICA, INC.
    2. Using the ST, push into the 5th-6th synchronizer hub.

      ST1 18651AA000 INSTALLER 

      ST2 398177700 INSTALLER 

      CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
      NOTE: When pushing into the 5th-6th synchronizer hub, move the 5th outer baulk ring to match the protrusion of the 5th outer baulk ring and the cut out of the 5th-6th drive gear bushing.
      G13648129Courtesy of SUBARU OF AMERICA, INC.
  17. Make sure that the 5th drive gear can be turned smoothly by hand. If it does not turn smoothly, reassemble.
  18. Attach the 5th-6th shifting insert at the appropriate position of the 5th-6th coupling sleeve.
    NOTE:
    • The location angle of each shifting insert is 120°.
    • Refer to the following figure to install the shifting insert key.
    G06346025Courtesy of SUBARU OF AMERICA, INC.
  19. Attach the 5th-6th coupling sleeve to the 5th-6th synchronizer hub.
    CAUTION: Apply transmission gear oil onto sliding or revolving surfaces before installation.
    NOTE:
    • There are two identification grooves on the 5th-6th coupling sleeve.
    • Place the grooves towards the 5th drive gear, and attach the 5th-6th coupling sleeve.
    G13648131Courtesy of SUBARU OF AMERICA, INC.
  20. Install the 6th baulk ring.
    G05003402Courtesy of SUBARU OF AMERICA, INC.
  21. Apply adequate transmission gear oil to the main shaft, 6th needle bearing and 6th drive gear inner surface.
  22. Install the 6th drive gear.
    G05003403Courtesy of SUBARU OF AMERICA, INC.
  23. Install the 6th needle bearing.
    G05003404Courtesy of SUBARU OF AMERICA, INC.
  24. With 6th drive gear bushing oil hole and the main shaft oil hole out of alignment, attach to the main shaft.
    G13648135Courtesy of SUBARU OF AMERICA, INC.
  25. Using the ST, install the 6th drive gear bushing.

    ST1 18651AA000 INSTALLER 

    ST2 398177700 INSTALLER 

    CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
    G05003406Courtesy of SUBARU OF AMERICA, INC.
  26. Make sure that the 6th drive gear can be turned smoothly by hand. If it does not turn smoothly, reassemble.
  27. Using the ST, install the double taper roller bearing inner race (front side).

    ST1 18651AA000 INSTALLER 

    ST2 398177700 INSTALLER 

    CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
    NOTE: Use a new double taper roller bearing.
    G05003407Courtesy of SUBARU OF AMERICA, INC.
  28. Using the ST, install the outer race and inner race (rear side) of the double taper roller bearing.

    ST1 18651AA000 INSTALLER 

    ST2 398177700 INSTALLER 

    CAUTION: Do not apply pressure in excess of 40 kN (4.0 ton, 4.4 US ton, 3.9 Imp ton).
    NOTE:
    • Confirm that the outer race and inner race are installed in the proper direction.
    • Push in until there is no backlash on the double taper roller bearing outer race and the bearing turns smoothly by hand.
    G13648138Courtesy of SUBARU OF AMERICA, INC.
  29. Make sure that the double taper roller bearing turns smoothly by hand. If it does not turn smoothly, replace the double taper roller bearing as a set, and reassemble.
  30. Attach a new lock washer and a new lock nut.
    CAUTION: Apply transmission gear oil to the lock washer and lock nut before installation.
  31. Set the main shaft assembly to the ST, and tighten the lock nut.

    ST1 18665AA000 HOLDER 

    ST2 18664AA000 BASE 

    NOTE: Make sure the lock washer is installed in the proper direction.

    Tightening torque: 

    392 N.m (40.0 kgf-m, 289.1 ft-lb)

    G13648139Courtesy of SUBARU OF AMERICA, INC.
  32. Using the ST, crimp the lock nut in 4 locations, with dimensions within A 27±0.3 mm (1.06±0.01 in).

    ST 18668AA000 PUNCH 

    NOTE: Do not damage the crimp area of the lock nut.
    G05003410Courtesy of SUBARU OF AMERICA, INC.
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