GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Transmission/Transaxle 🢒 Automatic Transmission - Allison 🢒 Transmission Replacement

Removal Procedure
  1. Block the front and rear wheels.
  2. Ensure the transmission is in neutral.
  3. Remove the shift lever assembly. Refer to Control Lever and/or Boot Replacement .

    4. Object Number: 816150 Size: SH
  4. Remove the floor plate screw and the floor plate.
  5. Raise and suitably support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  6. Remove the rear propeller shaft. Refer to One-Piece Propeller Shaft Replacement or Two-Piece Propeller Shaft Replacement in Propeller Shaft.
  7. Remove the clutch cable bracket. Refer to Clutch Cable Return Spring and/or Bracket Replacement .
  8. Remove the park brake cable. Refer to Park Brake Cable Replacement

    9. Object Number: 826892 Size: SH
  9. Disconnect the following electrical connectors:
    10. • Power take-off (PTO) relay , if equipped
    • Backup lamp switch
    • Vehicle speed sensor (VSS)
  10. Remove the transmission harness clips (1) from the harness brackets.
  11. Reposition the harness.
  12. Support the transmission with a suitable transmission jack.
  13. Remove the transmission bolts.
  14. Pull the transmission straight back on the clutch hub splines. Do not let the transmission hang from the clutch assembly.
  15. Remove the transmission from the vehicle.

Installation Procedure

    Notice: Refer to Fastener Notice in the Preface section.


    Object Number: 776275 Size: SH
  1. Position the transmission to the transmission housing. Do not use the transmission bolts to draw up the transmission.
  2. Install the transmission bolts.

    3. Tighten
    Tighten the transmission bolts to 260 N·m (192 lb ft).

  3. Remove the transmission jack.
  4. Install the clutch cable bracket. Refer to Clutch Cable Return Spring and/or Bracket Replacement .

    5. Object Number: 826892 Size: SH
  5. Position the harness.
  6. Install the PTO relay, connector, if equipped .
  7. Install the engine harness clips to the transmission.
  8. If equipped connect the following electrical connectors:
    9. • PTO relay, if equipped
    • Backup lamp switch
    • VSS
  9. Install the rear propeller shaft. Refer to One-Piece Propeller Shaft Replacement or Two-Piece Propeller Shaft Replacement in Propeller Shaft.
  10. Check and fill the transmission fluid.
  11. Lower the vehicle.
  12. Install the shift lever assembly. Refer to Shift Lever Assembly Replacement
  13. Install the park brake cable. Refer to Park Brake Cable Replacement