GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Blazer - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 233-NP1 (Two Speed Selectable) 🢒 Transfer Case Cleaning and Inspection

Front Case Half

    Object Number: 865830 Size: SH
  1. Clean the front case half and the input bearing retainer in cleaning solvent and air dry.

    2. Notice: Refer to Machined Surface Damage Notice in the Preface section.

  2. Remove the sealer from the case sealing surfaces.
  3. Inspect the case for being broken or cracked.
  4. Inspect the front output shaft front bearing bore (6) for the following conditions:
    5. • Spun bearing
    • Cracks
  5. Replace the front case half if any of the above conditions are found.
  6. Inspect the sealing surfaces (1 and 3) for damage.
  7. Repair small scratches or nicks with a soft stone.
  8. Inspect the front case to transmission case mounting surface for damage.
  9. Inspect the case threaded bolt holes (5) for damage.
  10. Repair any damaged threads.
  11. Inspect the retaining ring (4) of the annulus gear to ensure it is properly seated.
  12. Inspect the annulus gear (7) for the following conditions:
    13. • Damage or wear
    • Chipped gear teeth
    • Debris embedded in the root of the teeth
  13. Replace the front case half if the annulus gear is damaged.
  14. Inspect the sector shaft bore and seal for the following conditions:
    15. • Roughness
    • Excessive wear
  15. Replace the front case half if the sector shaft bore is faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble .
  16. Inspect the location pins for being loose or missing.
  17. Repair or replace any damaged location pins.
  18. Inspect the input shaft bearing bore (2) for the following conditions:
    19. • Spun bearing
    • Cracks
  19. Replace the input bearing retainer if faulty.
  20. Inspect the front output shaft front bearing and the input shaft bearing for the following conditions:
    21. • Roughness
    • Brinelling
    • Pitting
  21. Replace the bearings if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .

Rear Case Half

    Object Number: 865832 Size: SH
  1. Clean the rear case half, the extension, and the rear output shaft bearing retainer in cleaning solvent and air dry.

    2. Notice: Refer to Machined Surface Damage Notice in the Preface section.

  2. Remove the sealer from the case sealing surfaces.
  3. Inspect the parts for being broken or cracked.
  4. Replace the parts if they are broken or cracked.
  5. Inspect the sealing surfaces (2) for damage.
  6. Repair small scratches or nicks with a soft stone.
  7. Inspect the case threaded bolt holes for damage.
  8. Repair any damaged threads.
  9. Inspect the front output shaft rear bearing (3) for the following conditions:
    10. • Roughness
    • Brinelling
    • Pitting
  10. Replace the front output shaft rear bearing if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .
  11. Inspect the rear output shaft bearing for the following conditions:
    12. • Roughness
    • Brinelling
    • Pitting
  12. Inspect for a spun bearing bore (4) for the rear output shaft rear bearing.
  13. Replace the rear output shaft bearing retainer if a bearing has spun.
  14. Inspect the rear output shaft bushing (1) for scoring or wear.
  15. Replace the bushing if faulty.

Oil Pump

    Object Number: 865833 Size: SH
  1. Remove the oil pump suction pipe and the oil pump suction hose from the oil pump screen.
  2. Clean the pipe, hose, and screen in cleaning solvent and air dry.
  3. If the screen is embedded with debris, replace the screen.
  4. Inspect the hose for cracking or tears.
  5. Replace the hose if it is faulty.
  6. Inspect the oil pump for free movement.
  7. Replace the oil pump if there is any binding. Do not disassemble the oil pump. The oil pump is serviced as a unit.

Rear Output Shaft

    Object Number: 865835 Size: SH
  1. Clean the rear output shaft in cleaning solvent.
  2. Clean the rear output shaft oil galleries (2) and air dry.

    3. Important: Do not attempt to smooth any roughness in the bearing journals.

  3. Inspect the input gear pilot bearing surface (1) and the drive gear sleeve journal surface (4) for the following conditions:
    4. • Scoring
    • Pitting
    • Brinelling
    • Excessive wear
  4. Inspect the rear output shaft splines (3) for damage or excessive wear. Witness marks at the location of the gears are normal.
  5. Replace the rear output shaft if any of the above conditions are found.

High/Low Planetary Carrier

    Object Number: 886583 Size: SH
  1. Clean the high/low planetary carrier in cleaning solvent. Do not disassemble the planetary carrier.
  2. Air dry and ensure all cleaning solvent is removed from the bearings in the planetary gears (3). Do not spin the planetary gears with compressed air.
  3. Inspect the planetary gears for chipped teeth.
  4. Inspect the planetary gears for debris embedded in the root of the teeth.
  5. Inspect for a washer (4) being on each side of the planetary gears.
  6. Inspect the low range teeth (1) for damage or excessive wear.
  7. Inspect the thrust washer surface (2) for scoring or excessive wear.
  8. Replace the high/low planetary carrier if any of the above conditions are found.
  9. Inspect the high/low planetary thrust washers for excessive wear or scoring.
  10. Replace the thrust washers if they are faulty.

Drive Chain and Sprockets

    Object Number: 865836 Size: SH
  1. Clean the drive chain (1), drive sprocket (3), and driven sprocket (2) in cleaning solvent and air dry.
  2. Inspect the drive chain (1) for the following conditions:
    3. • Loose link pins
    • Binding or stiff links
    • Debris embedded in the links
    • Worn teeth surfaces
  3. Replace the chain if any of the above conditions are found.
  4. Inspect the driven sprocket (2) and the drive sprocket (3) for the following conditions:
    5. • Chipped teeth
    • Excessively worn gear surfaces
    • Slight wear marks are normal.
    • Debris embedded in the root of the teeth
  5. Replace the sprocket if any of the above conditions are found. The chain and sprockets may be replaced separately.
  6. Inspect the drive sprocket for the following conditions:
    7. • Roughness
    • Excessive wear
  7. Inspect the synchronizer engagement teeth on the drive sprocket for the following conditions:
    8. • Chips
    • Broken
    • Excessive wear
  8. Inspect the synchronizer blocking ring surface for wear or gouges.
  9. Replace the sprocket if faulty.

Front Output Shaft

    Object Number: 865837 Size: SH
  1. Clean the front output shaft in cleaning solvent and air dry.
  2. Inspect the front output shaft rear bearing race (2) for the following conditions:
    3. • Scoring
    • Pitting
    • Brinelling
    • Excessive wear
  3. Inspect the front output shaft splines (1) for damage.
  4. Replace the front output shaft if it is damaged.

Input Gear

    Object Number: 865838 Size: SH
  1. Clean the input gear, with pilot bearing, in cleaning solvent.
  2. Air dry and ensure all solvent is removed from the pilot bearing.
  3. Inspect the pilot bearing (1) for the following conditions:
    4. • Pitted
    • Wear
    • Corrosion
  4. Replace the input gear pilot bearing if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .
  5. Inspect the input gear engagement teeth (2) for chips.
  6. Inspect the input gear for broken or damaged planetary teeth (3).
  7. Inspect the input gear for debris embedded in the root of the teeth.
  8. Inspect the input gear seal surface (4) for pitting or excessive wear.
  9. Replace the input gear if any of the above conditions are found.

Shift System Components

    Object Number: 865839 Size: SH
  1. Clean the following shift system components in cleaning solvent and air dry:
    2. • The high/low shift fork (1)
    • The range sleeve (2)
    • The 2/4 wheel drive mode shift fork (3)
    • The shift fork shaft (4)
    • The sector shaft (5)
    • The synchronizer blocking ring (6)
    • The synchronizer assembly (7)
  2. Inspect the shift fork shaft for straightness (4).
  3. Replace the shift fork shaft if it is not straight.

    4. Object Number: 865840 Size: SH
  4. Inspect the pads on the 2/4 wheel drive mode shift fork for wear.
  5. Inspect the roller on the shift fork for wear.
  6. Replace the shift fork if the roller is worn or the pads are worn.

    7. Object Number: 865842 Size: SH

    Important: Only disassemble the shift fork assembly if replacing a faulty component.

  7. Inspect the following components of the high/low shift fork assembly for wear or damage:
    8. • The spring
    • The washers
    • The bracket
    • The shift fork
  8. Replace the high/low shift fork as an assembly if any of the above components are faulty.

    9. Object Number: 801271 Size: SH
  9. Inspect the range sleeve for chipped or excessively worn teeth (1).
  10. Inspect the shift fork collar (2) on the range sleeve for wear.
  11. Inspect the inner splines (3) of the range sleeve for excessive looseness on the rear output shaft.
  12. Replace the range sleeve if the above conditions are found.

    13. Object Number: 812485 Size: SH
  13. Inspect the high/low shift fork roller slot (2) on the sector shaft for wear or roughness.
  14. Inspect the bearing (1) and the seal surface on the sector shaft for the following conditions:
    15. • Pitted
    • Wear
    • Corrosion
  15. Inspect the 2/4 wheel drive mode shift fork cam lobes (3) on the sector shaft for wear or roughness.
  16. Inspect the detent plunger cam lobes (4) for wear or roughness.
  17. Replace the sector shaft if any of the above conditions are found.

    18. Object Number: 865843 Size: SH
  18. Inspect the synchronizer blocking ring (1) for wear and roughness.
  19. Inspect the synchronizer sleeve (2) for the following conditions:
    20. • Wear on the engagement teeth
    • Wear in the insert notches
  20. Inspect the synchronizer hub (4) for the following conditions:
    21. • Loose fit on the mainshaft
    • Broken or damaged insert springs (3 and 6)
    • Worn inserts (5)
  21. Replace the synchronizer assembly if any of the above parts are faulty.