Transfer Case Leak Diagnosis

WARNING: This page is about a different car, the 2008 GMC Sierra, 2008 GMC Cab & Chassis Sierra, 2008 Chevrolet Silverado, and 2008 Chevrolet Cab & Chassis 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 the correct amount of sealer on the plugs. Refer to Sealers, Adhesives, and Lubricants . Install the plugs correctly. Refer to Transfer Case Fluid Replacement .
Access hole plugs leaking	Replace the access hole plugs or seal with room temperature vulcanizing (RTV) sealer.
Vehicle speed sensor (VSS) leaking	Remove the VSS. Refer to Vehicle Speed Sensor Replacement . Inspect the VSS for the following conditions: Cross threaded Cut or damaged VSS O-ring seal VSS over tightened causing deformation in the VSS Replace the VSS O-ring seal if faulty. Replace the VSS if faulty.
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 rear output shaft seal. 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 . Replace the rear bushing if worn. Refer to Transfer Case Rear Extension Bushing Replacement . Replace the slip yoke if the surface could cause leakage. Refer to One-Piece Propeller Shaft Replacement or Two-Piece Propeller Shaft Replacement .
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 Leaking cup plug in the front output shaft 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 output shaft seal. Refer to Front Output Shaft Seal Replacement . Replace the front case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble . Replace the cup plug in the front output shaft if it is leaking. Refer to Transfer Case Disassemble and Transfer Case Assemble .
2/4 wheel drive actuator seal leaking	Replace the actuator seal. Refer to Transfer Case Two/Four Wheel Drive Actuator Replacement .
Leaking at the vent pipe	Transfer case overfilled Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement . Inspect for a damaged or missing vent pipe. Replace a damaged or missing vent and seal the vent pipe with the correct sealer. Refer to Transfer Case Assemble .
Transfer case to adapter leak	Inspect for the following conditions: Loose mounting fasteners Gasket faulty The transfer case input shaft seal leaking The pilot bearing in the input shaft leaking Repair or replace the following components if found faulty: Repair or replace the loose fasteners. Refer to Transfer Case Adapter Replacement . Replace the transfer case adapter gasket. Refer to Transfer Case Adapter Replacement . 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 Replace the pilot bearing in the input shaft if it is leaking. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Case leaking	Inspect for the following conditions: A cracked case Case porosity Replace the faulty case half. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Front case half to rear case half seam leak	Disassemble and seal the case halves. Refer to Transfer Case Disassemble and Transfer Case Assemble .