What is a Transfer Case Output Shaft Oil Seal?

Transfer cases are driven gear units that accept power input from the transmission output shaft, convert that to two separate outputs, and sometimes changes the output to a different speed than the transmission is spinning. Just like the shaft from the transmission, the two shafts that the transfer case uses to send power to the front and rear wheels are called output shafts. These are covered with oil inside the transfer case, but must have a means of keeping that oil from draining out of the output shaft housing. This is accomplished using a round rubberized seal known as the transfer case output shaft seal.


Part 7 of 7: Test drive the vehicle

Materials Needed

  • Flashlight

Step 1: Drive the vehicle around the block. While you are driving around, check to feel any abnormal vibrations. This may occur when the drive shaft could be out of timing.

Step 2: Check for oil leaks. When you are done with the test drive, grab a flashlight and look under the vehicle for any leaking oil. Look at the transfer case output shaft seal to see any leaking gear oil.

If your vehicle continues to leak oil from the transfer case after replacing the transfer case output shaft seal, then you may need to get a professional to take a look at the transfer case.

If the problem persists, get one of the certified technicians at YourMechanic to inspect the transfer case and diagnose the problem.

Part 2 of 7: Check the condition of the transfer case output shaft seal

Materials Needed

  • Flashlight
  • Non-lint cloth

Step 1: Grab a flashlight and look under the four-wheel drive vehicle for any oil on the ground. Then shine the light onto the transfer case output shaft and look to see if the seal is leaking.

Step 2: If the seal is leaking, use a non-lint cloth to clean it off. Visually check to see if the seal leaks slowly or fast.

How often do Transfer Case Output Shaft Oil Seals need replacement?

According to a comparison of real-world data, transfer case output shaft seals typically fail any time after 85,000 miles, with the majority of them failing long afterwards. Some failures are reported before the 85,000 mile mark, but that is typically not the case. Risk factors that could cause the output shaft seal to fail prematurely are lifted suspensions that alter the driveline angle, a worn drive shaft yoke, worn transfer case output shaft bearing, or lack of maintenance.


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