What Does A Transfer Case Do?

Transfer cases are auto parts commonly found in 4WD and some AWD vehicles like: Trucks, SUVs and Jeeps. A lot of drivers might not know if they have a transfer case under their car and how they wouldn’t be able to traverse certain terrain without it. Do you love off-roading or being able to drive on slippery surfaces with ease? Be sure to thank your transfer case! If you need to brush up on your general transfer case knowledge, you have come to the right place.

First, let’s go over the basics of what a drivetrain looks like on a 4WD and some AWD vehicles. It is the connection between your transmission and the drive shafts, power is sent from the transmission and to the transfer case. Torque is sent to the front and rear drive shafts to the axles, which are connected by differentials. The differential and axles send a certain amount of power to the drive wheels depending on the driving conditions. Some people get the transfer case confused with a differential, this is understandable because they have a similar purpose.

Transfer Case vs Differential 

2WD, 4WD and AWD vehicles have a differential but 4WD and some AWD vehicles have transfer cases too. A differential is between the two wheels in the front or the two in the back, depending on what type of drivetrain the car has. 4WD and AWD have a differential on the front and back axles. A differential allows both wheels to spin consistently at the same rate or it can distribute power to each wheel as needed. An example of this is when a wheel slips and loses traction. It transfers the power from the driveshafts to the axles, bringing power directly to the wheels. If you want to know more about how 4WD and AWD systems work you can read more about it in All Wheel Drive & Four Wheel Drive Explained.

How Does A Transfer Case Work?

It connects the transmission to the drive shafts, allowing the front axle and wheels to go different speeds than the back. Depending on the set up of the car and the driving conditions, the transfer case sends power to two wheels or all of them at once. Some vehicles with a transfer case have the ability to switch from 2WD to 4WD or AWD. 

The transfer case is similar to a differential and they have to work together to detect where the power and torque needs to be sent in the drive train. 4WD vehicles that are used more for off-roading have the ability to lock the front and rear axles together so the same amount of torque is sent to all the wheels. These 4WD vehicles are two-speed and have a low gear option so you can send more power to the wheels while traveling at slower speeds, this is the reason many people choose 4WD when they want to use a vehicle for offroading. You can climb rocks, travel rough terrain and carry heavy loads at slow speeds while having more torque sent to the wheels so the vehicle has these abilities. AWD vehicles are usually single-speed, they feel one of the wheels begin to slip or lose traction and send more power to that wheel. They are good for slippery surfaces but when the terrain gets rough, they won’t get the job done. 

The inside of your transfer case will either have a set of gears or a chain that drives the torque to the shafts. If it is a newer vehicle it is most likely a chain, some people prefer the older gear transfer cases because they can withstand more beating. As suspected, there is transfer case fluid to keep the gears lubricated, this is usually transmission fluid.

Part-time vs Full-time 

The transfer case is either part-time or full-time to put it in simple terms. Part-time transfer cases can switch between 2WD and 4WD. The 2WD in a part-time system is usually RWD and it takes added stress off the front components of the drivetrain when 4WD or AWD is not engaged, this also improves fuel economy. 

Full-time is when 4WD or AWD is engaged at all times, it sends the same amount of power to the front and back axles. The full-time transfer cases send different amounts of power to the front and back set of tires when it is needed because they have an extra center differential built into the transfer case. This way there isn’t unnecessary wear and tear or damage being done to your drivetrain and wheels. In full-time 4WD transfer cases, they have a locking center differential that can be engaged to force the front and back set of wheels to turn at the same speed. 

Nowadays it is not as simple as full-time vs part-time, many of these transfer cases can be controlled by the driver, who has the option to pick which terrain they are on or if they want to be in high or low gear. There are also systems that let the car detect the terrain and modify the drivetrain to adapt to the road conditions. 

Need A Replacement?

Sometimes car parts start to fail and we all know the feeling of getting that pricey bill from the mechanic. That’s why many people take up working on cars as a hobby, so they can fix their own vehicles for a fair price! You’re in luck because we know of a great used car parts store that has used parts that will fit your exact make and model. Ordering brand new auto parts online is pricey, especially for a vehicle that already has a good amount of mileage on it. Aftermarket and modified parts can be difficult to install, so it is best to go with used car parts. 
My Auto Store has a used transfer case that will fit perfectly into your drive train, they not only offer a 6 month warranty but have free online shipping! So don’t worry if your transfer case starts to go because used auto part stores like My Auto Store have you covered. Even if you don’t know how to work on cars, you might know someone who does. Ask them if you can pay them to replace it, while you buy the replacement car part for a decent price, this way it will still be much less money.