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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1781 (Automatic Transmission Overhaul - 4 Speed-Mu4) >> Repair Instructions >> Underdrive Clutch Assembly Replacement >> Removal Procedure

Removal Procedure

WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
  1. Inspect the underdrive one-way clutch before disassembly by placing the underdrive one-way clutch onto the rear of the underdrive clutch drum, holding the underdrive clutch drum stationary and rotating the underdrive one-way clutch.
  2. The underdrive one-way clutch should turn freely in a counterclockwise direction (2) and should not turn in a clockwise direction (3). If the underdrive one-way clutch is installed correctly on the underdrive clutch drum and the underdrive one-way clutch can be turned clockwise, replace the underdrive one-way clutch.
    Fig 1: Checking Underdrive One-Way Clutch Rotation
    G01384937Courtesy of GENERAL MOTORS CORP.
  3. Use a J 7872  to measure the underdrive clutch (1) piston stroke before disassembly.
    • Temporarily install the old underdrive clutch drum support seal rings on the underdrive clutch drum support in the transaxle case.
    • Place the underdrive clutch drum on the underdrive clutch drum support in the transaxle case and the J 7872  plunger on the underdrive clutch piston.
    Fig 2: View Of J 7872
    G01384938Courtesy of GENERAL MOTORS CORP.
  4. Apply 392-785 kPa (57-114 psi) of compressed air into the underdrive clutch apply passage (1) in the transaxle case and observe the J 7872 
    • The standard underdrive clutch piston stroke should fall within 1.500-1.900 mm (0.0590-0.0748 in).
    • If the underdrive clutch piston stroke is greater or less than specified, inspect all underdrive clutch components for excessive wear.
    Fig 3: Measuring Underdrive Piston Stroke Using Compressed Air
    G01384939Courtesy of GENERAL MOTORS CORP.
    CAUTION: Refer to SAFETY GLASSES CAUTION in Cautions and Notices.
    NOTE: The underdrive one-way clutch should be disassembled for inspection purposes only. If excessive wear or damage is found in any component of the underdrive one-way clutch upon inspection, replace the underdrive one-way clutch as an assembly.
  5. Remove the rear thrust plate (2) from the underdrive one-way clutch outer race (1).
    Fig 4: Removing Rear Thrust Plate
    G01384940Courtesy of GENERAL MOTORS CORP.
  6. Remove the underdrive one-way clutch retainers (2, 4) and the sprag assembly (3) from the underdrive one-way clutch outer race.
    Fig 5: Removing Underdrive One-Way Clutch Retainers & Sprag Assembly
    G01384941Courtesy of GENERAL MOTORS CORP.
  7. Remove the underdrive clutch snap ring (2) from the underdrive clutch drum (1).
    Fig 6: Removing Underdrive Clutch Snap Ring
    G01384942Courtesy of GENERAL MOTORS CORP.
  8. Remove the following components from the underdrive clutch drum (1):
    • The underdrive clutch flange
    • The 4 discs
    • The 4 plates
    Fig 7: Removing Underdrive Clutch Flange, Discs, & Plates
    G01384943Courtesy of GENERAL MOTORS CORP.
  9. Use a J 23327  with a J 37279  to remove the underdrive clutch piston return sprig snap ring (1) from the underdrive piston return spring (2).
    Fig 8: Removing Underdrive Clutch Piston Return Sprig Snap Ring
    G01384944Courtesy of GENERAL MOTORS CORP.
  10. Remove the following components from the underdrive clutch piston:
    • The underdrive clutch piston return spring (1)
    • The underdrive clutch piston return spring plate (2)
    Fig 9: Removing Underdrive Clutch Piston Return Spring & Spring Plate
    G01384945Courtesy of GENERAL MOTORS CORP.

    Important:  When using compressed air to remove components, air pressure should not exceed 98 kPa (14 psi).

  11. Remove the underdrive clutch piston from the underdrive clutch drum by placing the underdrive clutch drum on the underdrive clutch drum support in the transaxle case and applying low pressure compressed air into the underdrive clutch apply passage (1) in the transaxle case (2).
    Fig 10: Removing Underdrive Clutch Piston Using Compressed Air
    G01384946Courtesy of GENERAL MOTORS CORP.
  12. Remove the underdrive clutch drum from the underdrive clutch drum support in the transaxle case.
  13. Inspect the following components for excessive wear or damage and replace the underdrive one-way clutch assembly as necessary:
    • The underdrive one-way clutch sprag assembly
    • The underdrive one-way clutch outer race
  14. Inspect the underdrive clutch discs for excessive wear or damage and replace as necessary.
  15. Inspect the underdrive clutch piston for cracks or porosity and replace as necessary.
  16. Inspect the underdrive clutch piston check ball operation by applying compressed air into the working and release sides of the underdrive clutch piston.
  17. There must be no air leakage on the working side and air must pass freely through the release side. If these conditions do not exist, replace the underdrive clutch piston.
  18. Inspect the underdrive clutch piston return spring for distortion or weakness and replace as necessary.
  19. Use a J 26900-6  to measure the inside diameter of the front and rear underdrive clutch flange (3) bushings.
    • The standard underdrive clutch flange bushing diameter should measure within the following parameters:
      • Front (1) 46.500-46.525 mm (1.8307-1.8316 in).
      • Rear (2) 55.000-55.030 mm (2.1653-2.1665 in).
      Fig 11: Measuring underdrive clutch flange bushing diameter using J 26900-6
      G01384947Courtesy of GENERAL MOTORS CORP.
    • The maximum inside diameter of the underdrive clutch bushing should measure within the following parameters:
      • Front 46.570 mm (1.8334 in)
      • Rear 55.080 mm (2.1685 in)

        If the inside diameter of the underdrive clutch bushings are greater than specified, replace the underdrive clutch drum.

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