Transfer Case Leak Diagnosis

WARNING: This page is about a different variant/trim than selected.

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. See below for suggested diagnostic method(s).
Special Tools GE 28431-6 Fluorescent Oil Dye GE 28428-E High Intensity Black Light Kit For equivalent regional tools, refer to Special Tools . Fluorescent Dye Method Add GE 28431-6 Fluorescent dye to the transmission or transfer case to determine the source of the leak. Operate the vehicle. Inspect for the presence of dye within the oil leak using the GE 28428-E High Intensity Black Light Kit. A presence or non-presence of dye within the oil leak will indicate which component is the source of the leak. Powder Method CAUTION: Do not clean using brake cleaner or other reactive solvents as these solvents can damage rubber gaskets, seals and bushings. Thoroughly clean the suspected leak area using a rag. Apply an aerosol type leak tracing powder to the suspected leak area. NOTE: Do not drive the vehicle on the freeway as this will splatter oil inhibiting leak diagnosis. Operate the vehicle for 15-20 minutes under city driving conditions until normal operating temperatures are reached. Shut OFF the engine. Inspect the suspected leak area. Trace the leak path through the powder in order to find the source of the leak.
Drain plug or fill plug leak	Inspect for the correct sealer and amount of sealer on the plugs. Refer to Adhesives, Fluids, Lubricants, and Sealers . Correctly install the plugs. Refer to Transfer Case Fluid Replacement .
Access hole plugs leaking	Replace the access hole plugs or seal with room temperature vulcanizing (RTV) sealant.
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. For light duty vehicles, refer to Transfer Case Rear Extension Bushing Replacement . For heavy duty vehicles, refer to Transfer Case Disassemble , and Transfer Case Assemble . Replace the slip yoke if the surface could cause leakage. Refer to Rear 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 .
Transfer Case Overfill condition (Wet Cavity Applications)	Wet cavity adapter applications include transmission RPOs MW7/M99/M30/M32/M70. Dry cavity adapter applications include transmission RPOs MYC/MYD. If a transfer case overfill condition is present in a wet cavity adapter application, and the fluid level within the transmission is low, the source of the leak may be a faulty transfer case input shaft oil seal. Inspect transfer case for an overfill condition. Add J-28431-6 Fluorescent Dye to the transmission to determine if the transfer case input shaft oil seal is the cause of the overfill. Operate the vehicle Inspect the transfer case fluid for the presence of dye within the oil using the J-28428-E High Intensity Black Light Kit. If fluorescent dye is present within the transfer case fluid, replace the transfer case input shaft oil seal. Refer to Input Shaft Seal Replacement .