What Does a Transfer Case Do?

What Does a Transfer Case Do?
Pru Sanderson/Shutterstock

If you stop to think about vehicles with four-wheel drive (4WD) or all-wheel drive (AWD), it almost doesn’t make sense. How can one engine, in the front of the vehicle, power all four wheels? It turns out that your ability to move forward, turn and accelerate is dependent on what’s called a transfer case. But what is a transfer case, and how does it make AWD possible?

Most gas-powered AWD and 4WD vehicles have a transfer case that takes the engine power and distributes it to the rear and front wheels. When combined with front and back differentials, a transfer case makes it possible for the vehicle to put power to the wheels. Let’s dive in and see how it works.

What is a transfer case?

In vehicles with 4WD, the transfer case is a component that transfers power from the engine to the front and rear axles. The transfer case connects to the transmission and splits the power between the front and rear wheels.

There are two types of transfer cases: part-time and full-time. Part-time transfer cases only engage the 4WD when needed, such as when driving on a slippery or icy road. Full-time transfer cases are always involved and provide continuous power to all four wheels. They are found in AWD vehicles.

How does a transfer case work?

The transfer case contains gears that engage and disengage the front and rear wheels, depending on whether the vehicle is in two-wheel-drive or four-wheel-drive mode.

For most off-road-capable vehicles, the transfer case is controlled by a switch inside the vehicle. As a result, power is only sent to the rear axle when switched to the “2WD” position, ideal for driving on paved roads. In addition, two-wheel drive maximizes fuel efficiency and reduces wear and tear on the front axle and wheels.

Power is sent to both the front and rear axles when switched to the “4WD” position. This is ideal for driving on unpaved roads or off-road conditions because it provides better traction and stability.

The transfer case also contains a viscous coupling device that helps distribute power evenly to the front and rear wheels. This is important because it makes the vehicle less likely to get stuck in mud or snow.

How to maintain a transfer case

Like other components on your vehicle, transfer cases require regular checks and maintenance to work efficiently and as designed. Let’s look at four maintenance tips to extend the life of your transfer case.

1. Check the fluid level regularly. The transfer case needs lubrication, so make sure there is enough fluid. You can check the level by looking at the dipstick.

2. Change the fluid regularly. Like your engine oil, you should change the transfer-case fluid every few thousand miles. Changing the fluid regularly will help keep it running smoothly and prevent problems.

3. Be careful when off-roading. Avoid putting too much stress on the transfer case if you take your car off-road. Not all transfer cases are created equal, and most passenger-car transfer cases are built for control on the highway. Also, unlike a truck, your vehicle is designed for soft-roading and not heavy-duty off-roading use. So you may need to get a different vehicle if you do a lot of off-roading.

4. Get it serviced regularly. You should take your car to a mechanic for regular service, including getting the transfer case checked. They can spot any potential problems and fix them before they become serious.

By following these tips, you can help keep your transfer case in good shape and avoid significant problems. If you do have any issues, get them fixed right away so they don’t cause further damage.

Can you repair a bad transfer case?

Depending on time and your mechanical ability, replacing a transfer case is simple. However, since transfer cases are heavy, you’ll need a partner or two to assist you.

It’s essential to get a proper diagnosis from a professional mechanic if you choose to repair it yourself. What might seem like a complex repair may be an easily replaced electrical connection.

Trying to repair a bad transfer case yourself can further damage your vehicle if you’re unsure of what you’re doing. If you’re uncertain of your abilities, any complex repair should only be attempted by an experienced mechanic or professional.

Should you choose to have a professional repair, the average cost for transfer case replacement is between $2,511 and $2,624. Labor costs are estimated between $432 and $545, while parts cost an average of $2,079. Cost estimates will vary based on the vehicle, your location and other related repairs.


About Bumper

At Bumper, we are on a mission to bring vehicle history reports and ownership up to speed with modern times. A vehicle is one of the most expensive purchases you'll likely make, and you deserve to have access to the same tools and information the pros use to make the right decisions.

Disclaimer: The above is solely intended for informational purposes and in no way constitutes legal advice or specific recommendations.