S&T Series Blazer, Bravada, Envoy, Jimmy, Rainier, Trailblazer, Xtreme

Flywheel/Flexplate & Ring Gear

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General Information



On most of the engines covered by this manual the flywheel and the ring gear are machined from one piece of metal and cannot be separated. On some of the 4.3L engines the ring gear is a separate piece and can be driven from the flywheel once the gear is heated using a torch.

Removal & Installation



4.2L Engine
  1. Remove the transmission.
    NOTE
    Note the position and the direction of the engine flywheel before removal.

  2.  
  3. Remove the flywheel bolts.
  4.  
  5. Remove the flywheel.
  6.  
  7. Clean and Inspect the flywheel.
  8.  

To install:

  1. Add threadlock to the new flywheel bolts.

    Click image to see an enlarged view

    Fig. Flywheel bolt tightening sequence

  2.  
  3. Install the flywheel and secure the flywheel with the new bolts. Tighten the bolts in sequence, as follows:
    1. First pass: 18 ft. lbs. (25 Nm)
    2.  
    3. Final pass: An additional 50 degrees, with a torque angle meter
    4.  

  4.  
  5. Install the transmission.
  6.  

4.3L Engines
  1. Remove the transmission assembly from the vehicle.
  2.  
  3. If equipped with a manual transmission, remove the clutch and pressure plate assembly.
  4.  
  5. If equipped, remove the flywheel cover.
  6.  
  7. Remove the flywheel-to-crankshaft bolts, then remove the flywheel and spacer (if used) from the engine.

    Click image to see an enlarged view

    Fig. If a flywheel holding tool is not available install one of the transmission retaining bolts, then use a crowbar to prevent the flywheel from turning while loosening its bolts



    Click image to see an enlarged view

    Fig. After all the bolts have been unfastened, remove the flywheel



    Click image to see an enlarged view

    Fig. Remove the spacer or clutch housing cover (if equipped)



    Click image to see an enlarged view

    Fig. Use a torque wrench to tighten the flywheel bolts to specification



    Click image to see an enlarged view

    Fig. Installing the flywheel in the vehicle



    Click image to see an enlarged view

    Fig. View of the flywheel and related components (automatic transmission)



    Click image to see an enlarged view

    Fig. View of the flywheel and related components (manual transmission)

  8.  

To install:

  1. Inspect the flywheel for cracks, and inspect the ring gear for burrs or worn teeth. Replace the flywheel if any damage is apparent. Remove burrs with a mill file. Remove ant thread sealer from the flywheel bolts.
  2.  
  3. Install the spacer (if used) and the flywheel. Most flywheels will only attach to the crankshaft in one position, as the bolt holes are unevenly spaced and/or the crankshaft is fitted with a dowel pin.
  4.  
  5. Install the bolts and tighten to 74 ft. lbs. (100 Nm) using a crisscross pattern.
  6.  
  7. If equipped, install the clutch and pressure plate assembly.
  8.  
  9. Install the transmission assembly.
  10.  

5.3L Engine
  1. Remove the transmission.
  2.  
  3. Note the position and direction of the engine flywheel before removal.
  4.  
  5. Remove the engine flywheel bolts.
  6.  
  7. Remove the engine flywheel.
  8.  
  9. Clean and inspect the engine flywheel.
  10.  

To install:


NOTE
The flywheel does not use a locating pin for alignment and will not initially seat against the crankshaft flange, but will be pulled onto the crankshaft by the engine flywheel bolts. This procedure requires a three stage tightening process.

  1. Install the engine flywheel to the crankshaft.
  2.  
  3. Apply threadlock GM P/N 12345382 (Canadian P/N 10953489) or equivalent to the threads of the flywheel bolts.

    Click image to see an enlarged view

    Fig. Flywheel bolt tightening sequence-5.3L engine

  4.  
  5. Install the engine flywheel bolts. Tighten, in sequence, as follows:
    1. First pass: 15 ft. lbs. (20 Nm)
    2.  
    3. Second pass: 37 ft. lbs. (50 Nm)
    4.  
    5. Final pass: 74 ft. lbs. (100 Nm)
    6.  

  6.  
  7. Install the transmission.
  8.  

Ring Gear Replacement



4.3L Engines
  1. Remove the flywheel from the vehicle. Refer to the procedure outlined in this section.
  2.  
  3. Make certain that the ring gear is a separate piece, then using a torch, uniformly heat it around the entire circumference. DO NOT heat the gear until it is red hot as this will change the metal structure.
  4.  
  5. When the ring gear is hot enough, drive it off the flywheel using a hammer.
  6.  

To install:

  1. Using a torch, heat the ring gear uniformly until it expands enough to be installed on the flywheel.
    CAUTION
    Never heat the ring gear to a temperature above 400°F (204°C) as this will weaken the structure of the metal.

  2.  
  3. When the ring gear and flywheel have cooled sufficiently, install the flywheel on the vehicle.
  4.  

 
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