Transfer Case Leak Diagnosis

WARNING: This page is about a different car, the 2004 GMC Sierra and 2004 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

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	Inspect for the correct sealer and amount of sealer on the plugs. Correctly install the plugs. Refer to Transfer Case Fluid Replacement .
Vehicle speed sensor leaking	Remove the vehicle speed sensor (VSS) and inspect for the following conditions: Cross threaded Cut or damaged O-ring seal VSS over tightened causing deformation in the VSS Refer to Transfer Case Speed Sensor Replacement . Replace the VSS O-ring seal if faulty. Refer to Transfer Case Speed Sensor Replacement . Replace the VSS if faulty. Refer to Transfer Case Speed Sensor Replacement .
Rear output shaft seal leaking	Inspect for the following conditions: Overfilled or improper transfer case fluid Blocked vent Seal improperly installed, worn or damaged Seal bore damaged or cracked Rear output shaft bushing for excessive wear Slip yoke seal surface for wear or pitting Repair or replace the following components if found faulty: 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 Propeller Shaft Replacement - One Piece or Propeller Shaft Replacement - Two Piece in Propeller Shaft. Replace the rear bushing if worn. Refer to Transfer Case Output Shaft Seal Replacement - Rear . Replace the rear case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 149-NP3 Unit Repair. Replace the rear output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Rear .
Front output shaft seal leaking	Inspect for the following conditions: Overfilled or improper transfer case fluid Blocked vent Seal improperly installed, worn or damaged Seal bore damaged or cracked Repair or replace the following components if found faulty: 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 149-NP3 Unit Repair. Replace the front output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Front .
Leaking at the vent	Transfer case overfilled Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement . Inspect the transmission fluid level. Refer to Transmission Fluid Checking Procedure in Automatic Transmission - 4L60-E. If the transmission fluid level is low, and the transfer case fluid is too high, replace the transfer case input shaft seal. Refer to Transfer Case 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 Replace the vent if leaking at the case. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 149-NP3 Unit Repair.
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 149-NP3 Unit Repair.
Transfer case to adapter leak	Inspect for the following conditions: Loose mounting fasteners Gasket or sealant faulty The transfer case input shaft seal leaking Repair or replace the following components if found faulty: Replace the transfer case input shaft seal. Refer to Transfer Case 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 adapter gasket. Refer to Transfer Case Adapter Replacement .
Case leaking	Inspect for a cracked case or case porosity. Replace the faulty case half. Refer to Transfer Case Disassemble and Transfer Case Assemble in Transfer Case - NVG 149-NP3 Unit Repair.