A front output shaft bearing is a component that is commonly found on vehicles equipped with transfer cases, such as all wheel and four-wheel drive vehicles. The front output shaft bearing is the heavy duty bearing installed in the vehicle’s transfer case that supports and secures the front output shaft into place. The bearing keeps the shaft from wobbling as it rotates, and thus allows it to spin smoothly so that power can be transferred efficiently. While most output shaft bearings will usually last the life of the vehicle, they can sometimes be prone to issues that can cause issues with the operation of the vehicle. Usually a bad or failing front output shaft bearing will produce a few symptoms that can alert the driver of a potential issue.
1. Noisy drivetrain
One of the first symptoms of an issue with the vehicle’s front output shaft bearing is a noisy drivetrain. If the bearing becomes excessively worn or dries up, it can cause the drivetrain to make abnormal sounds when the four-wheel drive system is engaged. A worn or dried out bearing may produce howling or whining noises, and in more serious cases, even grinding noises. The sounds may change in volume or pitch according to the speed of the vehicle.
2. Excessive vibration from the drivetrain
Another common symptom of a possible problem with the vehicle’s output shaft bearing is excessive vibration from the drivetrain. A worn output shaft bearing can cause the output shaft to rotate unevenly and cause the drivetrain to produce excessive vibrations. The vehicle may experience excessive vibration when accelerating or cruising at a constant speed. The vibrations are also usually accompanied or preceded by noises as well.
3. Oil leaking from transfer case
Another symptom of a potential issue with the front output shaft bearing is oil leaking from the transfer case. Aside from supporting and securing the transfer cases front output shaft, the output shaft bearing also seals gear oil within the transfer case. If the output shaft bearing becomes damaged, it can cause gear oil to leak from the transmission. An oil leak from the transfer case will put the unit at risk of running low and suffering damage due to lack of lubrication.
While servicing the front output shaft bearing is not considered routine maintenance, it is a very important component to the proper operation of the transfer case. When it fails, this can cause issues with the vehicle’s drivetrain. If you suspect that your vehicle may be having an issue with the front transfer case bearing, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if the the car will need a front output shaft bearing replacement.
This article originally appeared on YourMechanic.com as Symptoms of a Bad or Failing Front Output Shaft Bearing and was authored by Eduardo Ruelas.