GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2006 🢒 GMC Sierra Denali 🢒 Preface 🢒 Cautions and Notices 🢒 Transfer Case Cleaning and Inspection

Front Case Half

    Object Number: 805636 Size: SH
  1. Clean the front case half 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 (3) for the following conditions:
    5. • Spun bearing
    • Cracks
  5. Inspect the input shaft bearing bore (5) for the following conditions:
    6. • Spun bearing
    • Cracks
  6. Replace the front case half if any of the above conditions are found.
  7. Inspect the sealing surfaces (1) for damage.
  8. Repair small scratches or nicks with a soft stone.
  9. Inspect the front case to transmission case mounting surface for damage.
  10. Inspect the case threaded bolt holes (4) for damage.
  11. Repair any damaged threads.
  12. Inspect the transmission to transfer case studs (2) for damage.
  13. Replace any damaged studs. Refer to Transfer Case Assemble .
  14. Inspect the location pins for being loose or missing.
  15. Repair or replace any damaged location pins.
  16. Inspect the front output shaft front bearing and the input shaft bearing for the following conditions:
    17. • Roughness
    • Brinelling
    • Pitting
  17. 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: 805640 Size: SH
  1. Clean the rear case half 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. Replace the case if it is broken or cracked.
  5. Inspect the sealing surfaces (1) 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 oil pump retainer (5) for wear or damage.
  10. Replace the oil pump retainer if faulty.
  11. Inspect the front output shaft rear bearing (4) for the following conditions:
    12. • Roughness
    • Brinelling
    • Pitting
  12. Replace the front output shaft rear bearing if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .
  13. Inspect the rear output shaft bearing for the following conditions:
    14. • Roughness
    • Brinelling
    • Pitting
  14. Inspect the rear output shaft rear bearing for a spun bearing bore.
  15. Replace the case if a bearing has spun.
  16. Inspect the rear output shaft rear bearing retaining ring (2) for being bent or twisted.
  17. Replace a faulty retaining ring.
  18. Inspect the rear output shaft bushing (3) for scoring or wear.
  19. Replace a faulty rear output shaft bushing. Refer to Transfer Case Disassemble and Transfer Case Assemble .

Oil Pump

    Object Number: 805643 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 the gears moving freely.
  7. Replace the oil pump if there is any binding in the gears.

Rear Output Shaft

    Object Number: 805644 Size: SH
  1. Clean the rear output shaft in cleaning solvent.
  2. Inspect the mainshaft rear bushing (1) in the rear output shaft for the following conditions:
    3. • Scoring
    • Pitting
    • Excessive wear
  3. Inspect the rear output shaft splines (3) for damage or excessive wear. Witness marks at the location of the gears are normal.
  4. Inspect the rear output shaft planetary gear (2) for the following conditions:
    5. • Chipped teeth
    • Broken teeth
    • Excessively worn teeth
  5. Replace the rear output shaft if any of the above conditions are found.

Mainshaft

    Object Number: 805654 Size: SH
  1. Clean the mainshaft in cleaning solvent.
  2. Clean the mainshaft oil galleries and air dry.

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

  3. Inspect the mainshaft front bearing journal (1) for the following conditions:
    4. • Scoring
    • Pitting
    • Excessive wear
  4. Inspect the mainshaft splines (2) for excessive wear. Witness marks on the splines are normal.
  5. Inspect the planetary sun gear bearing journal (3) for the following conditions:
    6. • Scoring
    • Pitting
    • Brinelling
    • Excessive wear
  6. Inspect the mainshaft rear bushing journal (4) for the following conditions:
    7. • Scoring
    • Pitting
    • Excessive wear
  7. Replace the mainshaft if any of the above conditions are found.
  8. Inspect the planetary sun gear bearing (5) for the following conditions:
    9. • Scoring
    • Pitting
    • Brinelling
    • Excessive wear
  9. Replace the planetary sun gear if it is faulty.

Differential Planetary Carrier

    Object Number: 886852 Size: SH
  1. Clean the differential 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 (2) being on each side of the planetary gears.
  6. Inspect the carrier teeth (1) for damage or excessive wear.
  7. Replace the differential planetary carrier if any of the above conditions are found.
  8. Inspect the differential planetary thrust washers for excessive wear or scoring.
  9. Replace the thrust washers if they are faulty.

Drive Chain and Sprockets

    Object Number: 801261 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.

Front Output Shaft

    Object Number: 805646 Size: SH
  1. Clean the front output shaft in cleaning solvent and air dry.
  2. Inspect the front output shaft rear bearing race (1) for the following conditions:
    3. • Scoring
    • Pitting
    • Brinelling
    • Excessive wear
  3. Inspect the front output shaft splines (2) for damage.
  4. Replace the front output shaft if it is damaged.

Input Gear

    Object Number: 805648 Size: SH
  1. Clean the input gear in cleaning solvent and air dry.
  2. Inspect the input bearing (1) for the following conditions:
    3. • Pitted
    • Wear
    • Corrosion
  3. Replace the input bearing if any of the above conditions are found. Refer to Transfer Case Disassemble and Transfer Case Assemble .
  4. Inspect the input gear seal surface (2) for pitting or excessive wear.
  5. Inspect the input gear thrust surface (3) for wear or damage.
  6. Inspect the cup plug inside of the input gear for leaking.
  7. Replace the input gear if any of the above conditions are found.

Viscous Coupling

    Object Number: 805650 Size: SH
  1. Inspect the viscous coupling for a bulged rear cover (1). The rear cover should be flat (2).
  2. Replace the viscous coupling if the rear cover is bulged.

Sun Gear and Annulus Gear

    Object Number: 805658 Size: SH
  1. Clean the sun gear (2) and the annulus gear (1) in cleaning solvent and air dry.
  2. Inspect the annulus gear (1) for the following conditions:
    3. • Damage or wear
    • Chipped gear teeth
    • Debris embedded in the root of the teeth
  3. Replace the annulus gear if any of the above conditions are found.
  4. Inspect the sun gear teeth for the following conditions:
    5. • Damage or wear
    • Chipped gear teeth
    • Debris embedded in the root of the teeth
  5. Inspect the planetary sun gear bearing journal in the sun gear for the following conditions:
    6. • Roughness
    • Brinelling
    • Pitting
  6. Inspect the sun gear thrust surfaces for scoring or roughness.
  7. Replace the sun gear if any of the above conditions are found.
  8. Inspect the planetary carrier sun gear thrust washer for scoring or wear.
  9. Replace the thrust washer if it is faulty.