Every four-wheel drive or all-wheel drive vehicle is equipped with a transfer case. But what exactly are transfer cases and what do they do? If this burning question has kept you up at night, you’ve come to the right place! Join us as we dive into the mysterious world of transfer cases, exploring their purpose and significance.
What is a transfer case?
If you have a four-wheel or all-wheel drive truck or SUV, you will find a component bolted to the back of your transmission known as the transfer case. This critical component is what is responsible for your vehicle’s ability to send power to both the front and rear wheels. The transfer case is in essence a power divider allowing the power that exits the rear of your transmission to go to either the rear wheels only or to both the front and rear wheels at the same time.
A modern transfer case is made up of several individual parts like shafts, bearings, gears, chains, external casing, etc. Certain all-wheel drive transfer cases are equipped with a built-in differential or viscous coupling, which enables the output shafts to rotate at varying speeds. This feature effectively prevents driveline bind when functioning properly.
Different kinds of transfer cases
There are several different types of transfer cases used in modern vehicles depending on the type of vehicle it is being used in and what type of functionality is being offered.
- Part-time four-wheel drive: This is the “traditional” transfer case most people think of when they think about a four-wheel drive vehicle. The part-time transfer case is the basic workhorse of the four-wheel drive world. These units will offer 2WD, 4HI, and 4LOW positions and can be shifted either manually with a shifter handle or electronically with electric controls on the dash. These units do not offer any type of torque biasing internally from built-in differentials or viscous couplings and cannot be used in four-wheel drive on dry surfaces.
- All-wheel drive: Transfer cases designed for AWD vehicles are equipped with an internal differential or viscous coupling, allowing power to be distributed to both the front and rear axles continuously. This means that AWD can be utilized even on dry pavement. Typically, AWD systems are commonly found in crossover SUVs and sedans.
- Active or on-demand four-wheel drive: A transfer case equipped with active or on-demand 4WD boasts a highly intricate design. Active 4WD essentially functions as an automatic 4WD system, eliminating the need for manual switching by the driver. Instead, the vehicle takes charge, activating 4WD when necessary based on the amount of wheel slip detected. To ensure optimal performance, electronic or mechanical methods are employed to regulate the power distribution to the front axle, effectively mitigating excessive wheel slip. These types of systems are not as strong as their part-time cousins and are in essence more accurately described as “traction control systems” rather than as a traditional, rugged four-wheel drive system.
Final thoughts
The modern four-wheel drive vehicle includes a complex system of mechanical and electronic components designed to offer a wide array of different functionality to today’s drivers. From the workhorse farm truck, to the rugged off-road rig, to the high end luxury SUV, there is a four-wheel drive system to get every job done!
Contact The Gear Shop if you have any questions
Need a replacement transfer case or just have a question? We are happy to help in any way we can!