Do you drive a 4WD or AWD car or SUV? Did you know that your vehicle had something called a transfer case? If not, you should. It’s a critical part of your drivetrain and is the reason you ever have torque in the right place on your axles while you’re driving. The fact is that the transfer case is one of those components that people may have vaguely heard of before but have no idea what it really is, what it does and how to know when this critical component is going wrong.

Hopefully, today’s blog will help enlighten readers and drivers of 4WD and AWD cars and offer some key insights into this important piece of your car’s drivetrain.

What is a Transfer Case in a Car?

Your car’s transfer case is a component that makes up part of the vehicle’s drivetrain. It’s attached to the transmission and connects the front and rear axles so that it can transfer torque from the transmission to each axle as needed. A more basic model may provide equal torque to all axles, but more advanced units can determine where torque is needed more and thus can manage the transfer by shifting different amounts of power to each axle as needed.

The main constituent components of this system are the input shaft, 2 output shafts and the housing usually made from iron, magnesium or aluminum.

How Does the Transfer Case Work?

While this may be your first time reading about your AWD transfer case, the way it works is actually quite straightforward. First of all, your car’s transmission will spin the input shaft around. The input shaft then splits the engine torque and power between both of the output shafts, one going to the front and the other to the rear.

Simple as it is, things can also go wrong with it. A well-built transfer case shouldn’t abruptly fail, but there are some warning signs that things aren’t quite right (see below for more). If your car has a part-time 4WD system then sometimes the unit simply might struggle to shift to 4WD or perhaps slips out of it. For AWD cases, faults in the components can translate into damage to other parts of your vehicle such as u-joints.

What are the Different Types of Transfer Case?

Broadly speaking, there are 3 types of transfer case that are in common use. They are:

• Part-time 4WD transfer case

• AWD transfer case

• Active 4WD transfer case

Part-Time 4WD Transfer Case

You might have a car that you can put into 4WD mode in certain situations, but the rest of the time is a regular 2-wheel drive system, either FWD or RWD. These transfer cases are often the most simple in design and don’t typically feature an internal differential. It’s quite a common feature on some entry-level trucks and SUVs where you might normally be driving in good conditions so you just need regular 2WD but then on occasions where the road gets slippery such as in winter, you can make the switch to 4WD as a temporary measure for more traction and control.

The lack of a differential actually makes it quite risky to drive using 4WD on regular road surfaces. The feature is specifically designed to increase traction in difficult conditions.

AWD Transfer Case

Unlike the part-time 4WD case, the AWD transfer case does have an internal differential that allows it to be used both in slippery conditions where traction is needed, and on regular dry road surfaces. That’s why it’s on at all times, moving torque to both axles. If you drive a modern crossover SUV or a larger sedan car you may have this kind of system.

Active 4WD Transfer Case

This type of transfer case is the most complex of the bunch. It’s not a permanent 4WD system, but rather a hugely upgraded version of the part-time 4WD system. When using it, the drivetrain system is able to detect when there isn’t enough torque in a particular axle and automatically activate 4WD to compensate.

Symptoms of a Bad Transfer Case?

Since most transfer cases are relatively simple in their construction — besides the Active 4WD case — there is therefore quite a bit less that can go wrong day to day. There are three main warning signs you should be looking for if you think the transfer case might be suffering.

Symptom 1: Grinding Noises

It seems that everywhere you look for information on signs that car components are going wrong there’s something about funny noises. With the transfer case it’s the same. Actually, there are many sounds that you might hear from the transfer case which are its regular functioning sounds, but the worrisome thing is that you shouldn’t be able to hear it. Hearing grinding could mean that the output shaft seal is broken, allowing internal noises to emerge.

Symptom 2: Trouble Shifting

If you are sensing some hesitation between shifting gears and those gears and torque kicking in, then it could well be because of an issue with the transfer case. The output shaft might be leaking or damaged, which diminishes the overall performance in the same way that an oil or coolant leak would do in your engine.

Symptom 3: Erratic 4WD

Does your vehicle keep shifting in and out of 4WD when it shouldn’t be? A faulty transfer case could be the problem. There could be a number of things in the transfer case going wrong that are causing the erratic 4WD performance, but whatever it is it needs to be fixed. It’s neither safe nor good for your car for it not to remain stably in the correct drive mode.

Conclusion: Tips for Maintaining Your Transfer Case

Good maintenance in your car’s transfer case is absolutely essential because driving with a faulty or otherwise bad transfer case is a very bad idea indeed. First of all, driving with the transfer case damaged will continue to damage it to the point where you can no longer repair it. Secondly, it’s unsafe because it means that your wheels might not be getting the right torque as needed, especially when added traction is needed. If it creates instability in your vehicle, it’s not safe.

Tip: Regular Checks

A good rule of thumb for transfer case maintenance is to have it checked every time you get an oil change. The intervals line up quite well and should mean you catch any developing issues early and can get them fixed before they become a more serious problem.

Tip: Stick to OEM Guidelines

If the OEM recommends a certain fluid or oil to make the transfer case work optimally, then use it. If it recommends maintenance at certain intervals, stick to it. OEMs don’t have a common transfer case that they all use. Each one is engineered slightly differently and so the OEM advice is based on that.

Tip: If You Have Chronic Issues, Swap It

If your transfer case is experiencing chronic issues, then swap it for another, even considering an aftermarket piece. There’s no point constantly repairing a transfer case if it’s really causing continuous problems. Replacing it is fairly straightforward.

Transfer Case Replacement Cost

Replacing the transfer case is relatively simple, but it’s costly. A fully new transfer case can cost between $430 and $550 for labor, plus another $2,000 for parts. If you can DIY the job, you can save a lot of money.

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