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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 Jimmy - 4WD 🢒 Driveline/Axle 🢒 Transfer Case - NVG 236-NP8 🢒 Transfer Case Leak Diagnosis

Cause

Correction

DEFINITION: A visible indication of an external fluid leak from the transfer case.

Review the Symptoms - Transfer Case and perform the necessary inspections.

Drain plug or fill plug leak
  1. Inspect for the correct sealer and amount of sealer on the plugs.
  2. Correctly install the plugs. Refer to Transfer Case Fluid Replacement .

Vehicle speed sensor leaking
  1. Remove the vehicle speed sensor (VSS) and inspect for the following conditions:
    2. • Cross threaded
    • Cut or damaged O-ring seal
    • VSS over tightened causing deformation in the VSS
  2. Replace the VSS O-ring seal if faulty. Refer to Transfer Case Speed Sensor Replacement .
  3. Replace the VSS if faulty. Refer to Transfer Case Speed Sensor Replacement .

Encoder motor area leak
  1. Remove the encoder motor and inspect for the following conditions:
    2. • Inspect the encoder motor insulator for cracks.
    • Inspect for a faulty control actuator lever shaft bearing.
    • Inspect the actuator lever shaft for wear or damage.
  2. Repair or replace the following components if found faulty.
    3. •  Replace the encoder motor insulator if cracked. Refer to Transfer Case Motor/Encoder Replacement .
    • Replace the control actuator lever shaft bearing if faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.
    •  Replace the control actuator lever shaft if the bearing or seal surface is faulty. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Rear output shaft seal leaking
  1. Inspect for the following conditions:
    2. • Overfilled or improper transfer case fluid
    • Blocked vent
    • Seal improperly installed, worn or damaged
    • Seal bore damaged or cracked
    • Rear bushing for excessive wear
    • Slip yoke seal surface for wear or pitting
  2. Repair or replace the following components if found faulty:
    3. • Adjust or replace the transfer case fluid. Refer to Transfer Case Fluid Replacement .
    • Clean or properly route the vent hose.
    • Replace the slip yoke if the surface could cause leakage. Refer to One-Piece Propeller Shaft Replacement or Two-Piece Propeller Shaft Replacement in Propeller Shaft.
    • Replace the rear bushing if worn. Refer to Rear Output Shaft Seal Replacement .
    • Replace the rear case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.
    • Replace the rear output shaft seal. Refer to Rear Output Shaft Seal Replacement .

Front output shaft seal leaking
  1. Inspect for the following conditions:
    2. • Overfilled or improper transfer case fluid
    • Blocked vent
    • Seal improperly installed, worn or damaged
    • Seal bore damaged or cracked
  2. Repair or replace the following components if found faulty:
    3. • Adjust or replace the transfer case fluid. Refer to Transfer Case Fluid Replacement .
    • Clean or properly route the vent hose.
    • Replace the front case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.
    • Replace the front output shaft seal. Refer to Front Output Shaft Seal Replacement .

Leaking at the vent

    • Transfer case overfilled
        1. Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement .
        2. Inspect the transmission fluid level. Refer to Transmission Fluid Check in Automatic Transmission - 4L60-E.
        3. If the transmission fluid level is low, and the transfer case fluid level is too high, replace the transfer case input shaft seal. Refer to Input Shaft Seal Replacement .
        4. Inspect for the following conditions:
   • Seal improperly installed, worn or damaged
   • Seal bore damaged or cracked
   • Input shaft seal surface worn, grooved or damaged
    • Replace the vent if damaged or broken and seal with the correct sealer if leaking at the case. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Transfer case to adapter leak
  1. Inspect for the following conditions:
    2. • Loose mounting fasteners
    • Gasket or sealant faulty
    • The transfer case input shaft seal leaking
  2. Repair or replace the following components if found faulty:
    3. • Replace the transfer case input shaft seal. Refer to Input Shaft Seal Replacement .
    • Inspect for the following conditions:
       - Seal improperly installed, worn or damaged
       - Seal bore damaged or cracked
       - Input shaft seal surface worn, grooved or damaged
    • Repair or replace the loose fasteners. Refer to Transfer Case Adapter Replacement .
    • Replace the transfer case gasket. Refer to Transfer Case Adapter Replacement .

Front case half to rear case half seam leak

Disassemble and seal the case halves. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.

Case leaking
  1. Inspect for a cracked case or case porosity.
  2. Replace the faulty case half. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 236-NP8 Unit Repair.