Transfer Case Leak Diagnosis

WARNING: This page is about a different car, the 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. 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 (TrailBlazer, Envoy, Rainier, Bravada) or Transfer Case Fluid Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV) .
Vehicle speed sensor leaking	Inspect the vehicle speed sensor (VSS) for the following conditions: Cross threaded Cut or damaged O-ring seal VSS over tightened causing deformation in the VSS Replace the VSS O-ring seal or the VSS if faulty. Refer to Transfer Case Speed Sensor Replacement - Front (TrailBlazer, Envoy, Rainier, Bravada) or Transfer Case Speed Sensor Replacement - Front (TrailBlazer EXT, Envoy XL, Envoy XUV) , Transfer Case Speed Sensor Replacement - Left Rear or Transfer Case Speed Sensor Replacement - Right Rear .
Rear output shaft seal leaking	Replace the rear output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Rear . Inspect the slip yoke seal surface for wear or pitting. Replace the slip yoke if the surface could cause leakage. Inspect the rear bushing for wear. Replace the rear bushing if the bushing is worn. Refer to Transfer Case Output Shaft Seal Replacement - Rear .
Front output shaft seal leaking	Replace the front output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Front (TrailBlazer, Envoy, Rainier, Bravada) or Transfer Case Output Shaft Seal Replacement - Front (TrailBlazer EXT, Envoy XL, Envoy XUV) . Inspect the front output shaft seal journal for wear. Replace the front output shaft if worn. Inspect the seal bore for damage. Replace the front case half if the seal bore is damaged.
Leaking at the vent tube	Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement (TrailBlazer, Envoy, Rainier, Bravada) or Transfer Case Fluid Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV) . 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 level is too high, replace the transfer case input shaft seal. Refer to Transfer Case Input Shaft Seal Replacement . Inspect the input shaft seal surface for wear or damage. Seal the vent tube with the correct sealer. Refer to Transfer Case Assemble in Transfer Case - NVG 226-NP8 Unit Repair.
Encoder motor area leak	Inspect the encoder motor insulator for cracks. Replace the encoder motor if the insulator is cracked. Refer to Transfer Case Motor/Encoder Replacement (TrailBlazer, Envoy, Rainier, Bravada) or Transfer Case Motor/Encoder Replacement (TrailBlazer EXT, Envoy XL, Envoy XUV) . Inspect for a faulty actuator lever shaft bearing. Replace the control actuator lever shaft if the bearing or seal surface is faulty. Replace the bearing if faulty. Refer to Transfer Case Assemble in Transfer Case - NVG 226-NP8 Unit Repair.
Transfer case to transmission area leak	Inspect the input shaft seal for leaking. Replace the input shaft seal if faulty. Refer to Transfer Case Input Shaft Seal Replacement . Inspect the input shaft seal surface for wear or damage. Inspect the front case seal bore for damage. Inspect for the input gear bore seal leaking. Replace the input gear bore seal if leaking. Refer to Transfer Case Assemble in Transfer Case - NVG 226-NP8 Unit Repair. Inspect the transmission adapter gasket for leaking. Replace the transmission adapter gasket if it is faulty. Refer to Transfer Case Assembly Replacement (TrailBlazer, Envoy) .
Front case half to rear case half seam leak	Disassemble and seal the case halves again. Refer to Transfer Case Assemble in Transfer Case - NVG 226-NP8 Unit Repair.