Most vehicles with all-wheel drive or four-wheel drive have a transfer case. The transfer case, located adjacent to the transmission, takes the power from the engine and distributes it to the front and rear wheels, so that you get better traction when you need it. This can include the following driving situations:

• Off-road driving
• Snowy, icy, muddy and rainy roads
• Steep inclines (going both up and down)

Transfer cases can be gear-driven or chain-driven. They can be separate units or may be integrated with the transmission. Some transfer cases are manually shifted, some are electronically shifted, and others require no driver involvement — hey engage automatically when extra traction is needed, and disengage when it is not.

Some transfer cases allow you to switch between two-wheel drive and four-wheel drive. Certain types even have specific gear settings that are designed for off-road use and shouldn’t be used for normal driving on paved roads. Check your owner’s manual for the guidelines on the proper use and control of your car’s transfer case.

What are the signs of a bad transfer case?

If your car has a transfer case, there are several signs that it might be failing. Let’s check the list:

Strange noises: You may hear one or more odd sounds coming from the transfer case, or from under your vehicle. These can include grinding, chattering or clicking. Any of these can indicate a bad transfer case. Call a mechanic and get your vehicle into the repair shop ASAP for diagnosis and repairs before the situation gets any worse.

Shifting gears becomes difficult: This can happen with both manual and automatic transmissions that work with transfer cases.

Your vehicle randomly disengages or engages its four-wheel drive: If you notice that your car will not keep its four-wheel drive engaged when you have it set, or it engages when it shouldn’t, there is a serious mechanical malfunction. It could be a bad transfer case. Contact a mechanic and have it fixed immediately.

Your transfer case will not shift at all: The transfer case’s inability to function whatsoever should tell you that you have a major problem. It’s time for a trip to the mechanic.

You notice a fluid leak on the ground, under your transfer case: If you see fluid leaking from the area of your transfer case, call your mechanic as soon as you can to see whether it is safe to drive. It may be less damaging to have your car towed to the repair shop, as opposed to trying to drive it there.

You smell something burning: A bad transfer case can cause low fluid levels, which may result in excess friction inside the transfer case. The smell of burning fluid is very noticeable, and should send you right to your mechanic.

Your check engine or service 4WD light comes on: The high internal temperatures from a bad transfer case can cause your engine computer to trigger the check engine or service 4WD lights on your dashboard. Your mechanic can find the source of the problem.

Should you drive your car with a bad transfer case?

Driving your car with a bad transfer case is a bad idea. If you continue to drive with a transfer case that has a serious mechanical problem, you could destroy it beyond the point of repair, and possibly damage your transmission, driveshafts and axles in the process.

How do you fix a bad transfer case?

The exact answer to this depends on how extensive the damage to your bad transfer case is, and whether it can be repaired or not:

If your bad transfer case can be repaired: A mechanic can replace any damaged or defective parts, replace the seals, and add fresh fluid. The final step will be to test the transfer case for correct operation.

If your bad transfer case cannot be repaired: A mechanic will replace your bad transfer case with a remanufactured one, which will work as well as a new one, and should also come with a warranty.

Can you replace a bad transfer case by yourself?

Unless you have expertise in dealing with heavy, complex automotive driveline components like transfer cases, you are much better off leaving this job to a professional mechanic. Once your transfer case has been repaired, the mechanic will check that your transmission and drive system are ready for further adventures.

About the Author

Stephen has been an automotive enthusiast since childhood, owning some of his vehicles for as long as 40 years, and has raced open-wheel formula cars. He follows and writes about the global automotive industry, with an eye on the latest vehicle technologies.