A transfer case is only made for all-wheel drive and four-wheel drive cars, sending power from the engine to the rear wheels. The transfer case is a sealed unit and can be either gear-driven or chain-driven depending on the manufacturer. Because the transfer case is a sealed unit, it needs lubrication to keep all of the moving components clean and at a reasonable temperature. Transfer case fluid allows the longevity of parts in the transfer case.

How this system works:

In four-wheel drive and all-wheel drive vehicles, a transfer case is either linked directly to the back of the transmission, or by a small driveshaft further back in the car. When activated, the transfer case takes power from the engine to the back wheels. Depending on the kind of car, power may go to the rear wheels on a full-time or part-time basis. All-wheel drive systems are typically on all of the time while a four-wheel drive system are activated by either pressing a button in the car or by manipulating a selector lever, typically found near the transmission hump on the floor. In both systems, transfer case fluid keeps the internal parts of the transfer case lubricated. Over time, transfer case fluid will get dirty and break down. When transfer case fluid breaks down you may see shuddering from the vehicle while turning or a whining noise from the gears in the transfer case.

Common reasons for this to happen:

  • Time:Over time, transfer case fluid will break down and become dirty. Dirty transfer case fluid may make moving parts in the transfer case to have more difficulty moving, which may cause them to fail.
  • Improper Filling:If the transfer case is not properly filled with transfer case fluid, it may go down more quickly, have difficulty dissipating heat, and keeping parts lubricated.

How it’s done:

A mechanic will first have your car idle for a few minutes to warm the fluid as warm fluid will drain easier. The mechanic will then drain the old transfer case fluid through the drain plug. The drain plug on most transfer cases is magnetic and picks up metal shavings that otherwise might potentially damage parts in the transfer case. The mechanic should clean the drain plug before changing it. The mechanic will then take out the fill plug and add new fluid. The mechanic should also double-check the amount of fluid, he or she puts in the transfer case, making sure that it was done properly. A car that is under-lubricated may not dissipate heat or protect critical components as well as a vehicle that is properly lubricated. When the transfer case is full, the mechanic will change the fill plug and check for any leaks.

How vital is this service?

By choosing to not to change your transfer case fluid, you may compromise critical and expensive parts inside the transfer case. Because the transfer case is a sealed unit, it is very vital that the transfer fluid is filled properly so that heat is appropriately dissipated and parts to not suffer from unneeded friction. Repairing a differential can be very expensive, so in order to preserve these components, you should have you transfer case fluid changed at the correct intervals. Doing so could potentially save you a lot of money and stress down the road.H