Transfer Case Leak Diagnosis

WARNING: This page is about a different car, the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. 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.
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 bushing if it is worn.
Speed sensor leaking	Replace the O-ring seal on the speed sensor. Refer to Transfer Case Speed Sensor Replacement (Front) or Transfer Case Speed Sensor Replacement (Right Rear) or Transfer Case Speed Sensor Replacement (Left Rear) .
Front output shaft seal leaking	Replace the front output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Front . 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 . Inspect the transmission fluid level. Refer to CHECKING FLUID LEVEL & CONDITION (4L60-E) or CHECKING FLUID LEVEL & CONDITION (4L80-E) . If the transmission fluid level is low, replace the transfer case front input shaft seal. Refer to Transfer Case Input Shaft Seal Replacement . Inspect the front input shaft seal surface for wear or damage. Reseal the vent tube with the correct sealer. Refer to Transfer Case Assemble in Transmission, Transaxle Unit Repair manual.
Motor/encoder area leak	Inspect the motor/encoder insulator for cracks. Replace the motor/encoder if the insulator is cracked. Refer to Transfer Case Motor/Encoder Replacement . 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 it is faulty. Refer to Transfer Case Assemble in Transmission, Transaxle Unit Repair Manual.
Transfer case to transmission area leak	Inspect the front input shaft seal for leaking. Replace the front input shaft seal if it is faulty. Refer to Transfer Case Input Shaft Seal Replacement . Inspect the front 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 it is leaking. Refer to Transfer Case Assemble in Transmission, Transaxle Unit Repair Manual. Inspect the transmission adapter gasket for leaking. Replace the transmission adapter gasket if it is faulty. Refer to Transfer Case Adapter Replacement .
Front case half to rear case half seam leak	Disassemble, and reseal the case halves. Refer to Transfer Case Assemble in Transmission, Transaxle Unit Repair Manual.