Transfer Case Leak Diagnosis

WARNING: This page is about a different car, the 2007 Isuzu i-370, 2007 GMC Canyon, and 2007 Chevrolet Colorado. 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 the drain or fill plug gasket for being faulty. Install the plugs correctly. Refer to Transfer Case Fluid Replacement .
Hole plug leaking	Replace the access hole sealer.
Vehicle speed sensor (VSS) leaking	Remove the VSS. 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 Front Propeller Shaft Replacement , Propeller Shaft Replacement - One Piece or Propeller Shaft Replacement - Two Piece . Replace the rear bushing, if worn. Refer to Transfer Case Disassemble and Transfer Case Assemble . Replace the rear case half if the seal bore is damaged. Refer to Transfer Case Disassemble and Transfer Case Assemble . Replace the rear output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Rear .
Front output shaft area leak	Inspect for the following conditions: Overfilled or improper transfer case fluid Blocked vent Loose yoke flange nut Missing or damaged yoke flange O-ring seal Yoke flange seal surface worn or damaged 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 . Replace the yoke flange nut and O-ring seal if loose. Refer to Transfer Case Output Shaft Seal Replacement - Front . Replace the front output shaft seal. Refer to Transfer Case Output Shaft Seal Replacement - Front . Replace the front yoke flange if seal surface is faulty. Refer to Transfer Case Output Shaft Seal Replacement - Front .
Control actuator shaft seal leaking	Replace the control actuator shaft seal. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Leaking at the vent tube	Transfer case overfilled Inspect for the correct transfer case fluid level. Refer to Transfer Case Fluid Replacement . Replace a damaged or broken vent and seal the vent pipe with the correct sealer. Refer to Transfer Case Assemble .
Leak at transfer case adapter weep hole - automatic transmission only	Inspect for the following conditions: Transmission fluid level low Refer to Transmission Fluid Checking and Transfer Case Fluid Replacement . Transmission rear seal for leaking Transfer case input shaft seal for leaking Cup plug in transfer case input shaft for leaking Repair or replace the following components, if found faulty: Replace the transmission rear seal, if leaking. Refer to Transmission Extension Housing Rear Oil Seal Replacement . 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 cup plug in the input shaft if leaking. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Leak at transfer case mounting weep hole - manual transmission only	Inspect for the following conditions: Transmission fluid level low Refer to Transmission Fluid Replacement and Transfer Case Fluid Replacement . Transmission rear seal for leaking Transfer case input shaft seal for leaking Cup plug in transfer case input shaft for leaking Repair or replace the following components, if found faulty: Replace the transmission rear seal if leaking. Refer to Transmission Housing Oil Seal Replacement - Rear (4WD)Transmission Housing Oil Seal Replacement - Rear (RWD) . Replace the transfer case input shaft seal if leaking. 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 input shaft if the seal surface is worn. The rear output shaft seal, of the manual transmission, seals on the input shaft of the transfer case. Refer to Transfer Case Disassemble and Transfer Case Assemble . Replace the cup plug in the input shaft, if leaking. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Case leaking	Inspect for a cracked case or 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 Assemble .
Switch leaks	Remove the NEUTRAL switch or 2/4 indicator switch, if leaking. Inspect for a faulty gasket. Replace the faulty switch gasket. Refer to Transfer Case Neutral Switch Replacement or Transfer Case 2/4 Indicator Switch Replacement .
Shift shaft detent plug leaking	Inspect the leaking plug for the following conditions: Proper sealant Stripped or damaged threads on the plug or the case. Incorrectly tightened Replace the detent plug, if faulty, and install correctly. Refer to Transfer Case Disassemble and Transfer Case Assemble .
Shift shaft plugs leaking	Replace the leaking shift shaft plug. Refer to Transfer Case Disassemble and Transfer Case Assemble .