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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 19 (Automatic Transmission - ALLISON - Introduction (2 Of 2)) >> Repair Instructions >> Transmission Replacement (With 8.1L (L18) Engine) >> Removal Procedure

Removal Procedure

WARNING: This page is about a different variant/trim than selected.
IMPORTANT: If replacing a failed transmission, the "Fast Learn" (adapt) procedure must be performed. This can be done in one step using a scan tool. If this procedure is not done, the transmission control module's (TCM's) adaptive valves will be at the settings that it learned for the old transmission, and will be in slow adaptive mode. Under these conditions, it would take an unacceptably long time for the adaptive values to converge to levels suitable for the new transmission.
  1. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure (Single Battery) or Battery Negative Cable Disconnect/Connect Procedure (Auxiliary Battery) in Engine Electrical.
  2. Remove the transmission fluid level indicator.
  3. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Remove the engine protection shield bolts and shield.
    Fig 1: Identifying Engine Shield And Retaining Bolts
    GM310119Courtesy of GENERAL MOTORS CORP.
  5. Remove the starter motor bolts and position the starter motor aside.
    Fig 2: Removing Starter Motor (8.1L)
    GM747161Courtesy of GENERAL MOTORS CORP.
  6. Drain the transmission fluid, if necessary.
  7. If the vehicle is a 2 wheel drive (2WD), remove the propeller shaft. Refer to Propeller Shaft Replacement - One Piece orPropeller Shaft Replacement - Two Piece in Propeller Shaft.
  8. Support the transmission with a transmission jack.
  9. If the vehicle is a 2WD, remove the transmission mount nuts.
    Fig 3: Identifying Transmission Mount Nuts
    GM647997Courtesy of GENERAL MOTORS CORP.
  10. If the vehicle is a 2WD, remove the transmission support bracket bolts.
    Fig 4: Identifying Crossmember & Bolts
    GM652595Courtesy of GENERAL MOTORS CORP.
  11. If the vehicle is a 2WD, remove the transmission support bolts and nuts.
  12. If the vehicle is a 2WD, remove the transmission support.
  13. If the vehicle is equipped with 4 wheel drive (4WD), remove the transfer case.
  14. Remove the transmission mount bolts (1).
    Fig 5: Locating Transmission Mount Bolts
    GM702771Courtesy of GENERAL MOTORS CORP.
  15. Remove the transmission mount.
    16. Fig 6: Disconnecting Shift Cable From Selector Lever Ball Stud (8.1L)
    GM686691Courtesy of GENERAL MOTORS CORP.
  16. Disconnect the shift cable from the selector lever ball stud (5) and remove the cable from the bracket (3).
    17. Fig 7: Removing Shift Cable Bracket Bolts And Bracket
    GM686689Courtesy of GENERAL MOTORS CORP.
  17. Remove the shift cable bracket bolts and bracket (2) from the transmission.
    18. Fig 8: Disconnecting Speed Sensor Electrical Connectors
    GM702774Courtesy of GENERAL MOTORS CORP.
  18. Disconnect the turbine speed sensor (1) and input speed sensor (2) electrical connectors.
  19. Disconnect the output speed sensor (3) electrical connector. If the vehicle is equipped with 4WD, the output speed sensor is located on the transfer case and will already be disconnected.
    20. Fig 9: Disconnecting External Wiring Harness From Transmission Main Connector
    GM659284Courtesy of GENERAL MOTORS CORP.
  20. Disconnect the transmission main electrical connector. J 44257  may be used, but is not required. See Special Tools .
  21. Disconnect the park neutral position (PNP) switch electrical connector.
    22. Fig 10: Removing Fuel Line Retainer Bolts
    GM702521Courtesy of GENERAL MOTORS CORP.
  22. Remove the fuel line retainer (1) bolts on the left side of the transmission.
    23. Fig 11: Removing Heat Shields
    GM744180Courtesy of GENERAL MOTORS CORP.
  23. Remove the transmission heat shield bolt and nut (4, 5) and shield (3).
    24. Fig 12: Removing Exhaust Pipe Hanger Bracket
    GM694239Courtesy of GENERAL MOTORS CORP.
  24. Remove the exhaust pipe hanger bolts and reposition the hanger.
    25. Fig 13: Removing Heat Shields
    GM744180Courtesy of GENERAL MOTORS CORP.
  25. Remove the transmission heat shield bolts (2) and shield (1).
    26. Fig 14: Removing Converter Housing Inspection Cover (8.1L)
    GM686693Courtesy of GENERAL MOTORS CORP.
  26. Remove the converter housing inspection cover bolts and cover.
  27. Rotate the engine clockwise, using the crankshaft bolt in order to access the torque converter bolts thru the starter opening. Have an assistant rotate the engine while aligning the bolts.
  28. Remove the torque converter bolts (3).
    Fig 15: Removing Torque Converter Bolts (8.1L)
    GM686680Courtesy of GENERAL MOTORS CORP.
    29. Fig 16: View Of Fill Tube To Bellhousing Nuts
    GM702776Courtesy of GENERAL MOTORS CORP.
  29. Remove the transmission fill tube nuts from the converter housing studs.
    30. Fig 17: Removing Fuel Line Bracket Nut
    GM702523Courtesy of GENERAL MOTORS CORP.
  30. Remove the fuel line bracket nut from the converter housing stud.
    31. Fig 18: Removing Wire Harness/Vent Tube Bracket Nut
    GM702529Courtesy of GENERAL MOTORS CORP.
  31. Remove the wire harness/vent tube bracket nut from the converter housing stud and reposition the bracket.
    32. Fig 19: Securing Safety Chain Around Transmission
    GM702527Courtesy of GENERAL MOTORS CORP.
  32. Secure a safety chain around the transmission. Use care not to overlap any wiring, fuel lines, or other related components.
    33. Fig 20: Disconnecting Transmission Oil Cooler Lines From Transmission
    GM686709Courtesy of GENERAL MOTORS CORP.
  33. Disconnect the transmission oil cooler lines (1, 2) from the transmission.
  34. Plug the transmission oil cooler line fittings in the transmission case.
  35. If the vehicle is equipped with a power take off unit (PTO), disconnect and/or remove any necessary components to facilitate transmission removal.
    36. Fig 21: Removing Converter Housing Bolts And Studs (8.1L)
    GM744182Courtesy of GENERAL MOTORS CORP.
  36. Remove the remaining converter housing bolts and studs.
  37. Separate the transmission from the engine.
  38. InstallJ 21366  to the converter housing in order to keep the torque converter from sliding off of the turbine shaft.
    Fig 22: Installing J 21366 To Converter Housing
    GM702530Courtesy of GENERAL MOTORS CORP.
  39. Carefully lower the transmission from the vehicle while simultaneously removing the fill tube.
  40. Remove the J 21366  .
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