Used Transfer Case
If you have a four-wheel-drive or all-wheel-drive vehicle, one of the key components of your power train is the used transfer case. It is a heavy-duty piece of power transfer hardware, just like your transmission. It functions similarly to what industrial or farm machine operators might refer to as a “power take-off,” which gives you a clue to its purpose. A used transfer case takes power off of your main drive shaft – the one that drives two of the wheels on your car – and transfers that power to the other two wheels, so all wheels are driven by the engine through the transmission.
How it Works
Standard four-wheel-drive vehicles have a drive shaft that sends rotational power from the transmission to the rear wheels. This shaft will pass through the transfer case. In two-wheel-drive mode, these trucks or SUVs will propel themselves by connecting engine power to the rear wheels only. If the operator or vehicle control system shifts into four-wheel drive, the transfer case will engage a second drive shaft that sends the power forward to the front wheels as well. In older manually shifted cars or trucks, the driver actually moved a lever or handle to engage the mechanical power transfer linkage in the transfer case, similar to shifting a manual transmission with a stick shift. Modern vehicles are more likely to have an electric solenoid that will engage the transfer case four-wheel-drive function at the touch of a button, or even automatically if wheel slip is detected in two-wheel drive mode.
What it Looks Like
Transfer case design varies from vehicle to vehicle, but the unit generally appears as two heavy castings bolted together, with three drive shaft connections (one for the transmission shaft, and one shaft each for front and rear wheels). A transfer case may contain a hundred or so parts, if you include all the bolts that hold it together. The internal components that do the heavy work are finely machined gears and shafts that transfer the rotational power of the main drive shaft to the secondary drive for the wheels that just coast when not in four-wheel-drive mode. Some transfer cases make this power connection with a series of heavy duty gears, others use a sturdy chain-and-gear system, similar to a motorcycle chain and sprockets, but much heavier and slightly different in design.
If you have a four- or all-wheel-drive car or truck that has lost its four-wheel pulling power, it’s possible your transfer case is the culprit. This can be bad news if you plan to replace the transfer case with a new unit; they can cost $1,500 to $1,700 or more, depending on your vehicle specifications. The good news is that a used transfer case is often available at a substantial cost savings over buying a new one. Auto recyclers are likely to have a large selection, because auto-body-crumpling collisions often leave a used transfer case undamaged and available for resale.
If you’ve been unlucky enough to experience a transfer case failure, don’t despair. You could be saved from the financial disaster you might be fearing, because the right used transfer case is as close as a phone call away.