A transfer case is a viscous coupling, a center differential or another arrangement of gears designed to handle a speed difference between front and rear wheels in all-wheel drive and four-wheel drive vehicles. Usually located next to the transmission, it allows for power distribution between the front and rear axles for better traction on snow, icy and rainy roads as well as harsh terrains. A transfer case delivers high torque to the drive wheels at very low speeds, which makes it possible to conquer steep hills and other off-road conditions.
Not all transfer cases are the same. While most of them are chain or belt driven and come as a separate assembly, some transfer cases can be integrated with a transmission. Besides, some of them are manually or electronically operated and controlled by a driver, while others are automatically engaged when extra traction is required. You may also find transfer cases that can be switched between the two-wheel drive mode and the four-wheel drive one, and even those transfer cases which provide a specific set of gears for severe off-road conditions.
A transfer case is a major drivetrain component of any four-wheel drive or all-wheel drive vehicle. Its failure can cause you to leave your vehicle on the roadside until it gets towed to a repair shop. To avoid that stressful experience, you should know the most common signs of a failing transfer case.
Abnormal noises from the transfer case area
Any grinding, clicking, or chattering sounds coming from your transfer case or from under the vehicle can be a sign of a failing transfer case. If so, you should get in touch with your mechanic for advice and have your vehicle towed to a repair shop if needed to prevent damage to the transfer case or the rest of the drivetrain.
It’s hard or impossible to change a gear
This symptom can be caused by a malfunctioning transfer case no matter what type of transmission you have.
Your vehicle switches from two-wheel drive to four-wheel drive on its own
If it happens you can’t activate or disengage the four-wheel drive mode, or this happens randomly, your transfer case can be the root of the problem. Don’t ignore this symptom as it may cause severe damage to the transfer case.
Your transfer case fails to function
This is a major problem which means you have missed other signs of a failing transfer case.
Fluid leaks on the transfer case or underneath the car
A leaking transfer case can lead to an array of problems. If you want to save a lot of headache, call your mechanic as soon as the first leak is detected.
Smell of burning fluid
If you have a huge fluid leak, the level of hydraulic fluid in the transfer case can reach a critical point. This will increase friction between the moving parts inside the case, resulting in overheating and burning fluid.
Illuminated check engine light or service four-wheel drive light
A malfunctioning transfer case may operate at higher than normal temperatures, which can cause the powertrain control module to turn on the check engine light or service four-wheel drive light.
What should I do if I have a bad transfer case?
A faulty transfer case can not only cause severe damage to the transmission, axles and other drivetrain components, but also put your life at risk. That’s why driving with a bad transfer case is an experience you should avoid.
As soon as you notice any sign of a failing transfer case, you should have it inspected by a professional. Depending on the condition of the transfer case, your mechanic can offer you either to replace all defective parts and refill your transfer case with fresh fluid or to replace it with a remanufactured or brand-new assembly if yours is not repairable.
We would not recommend you to replace or repair a transfer case yourself if you have never dealt with drivetrain components like transmissions or transfer cases. You should leave this job to a qualified mechanic.