If you drive a four-wheel drive vehicle, you probably know what a transfer case is. What you may not be aware of is that there are several different types of transfer cases, depending on the drive type, housing and the way that it shifts. There is also some maintenance that may be required for your transfer case, and it’s best to be aware of that so that you can keep it in top working order and prevent costly repairs down the road.
What Transfer Cases Do
A transfer case takes power from the transmission and sends it to both the front and rear wheels. For on-road vehicles, it will also synchronize the rotation of the front and rear wheels. Some of these mechanisms also contain low range gears that can be engaged for extreme off-roading at slower speeds.
Drive Types
Transfer cases are either gear-driven or chain-driven. The gear-driven variety can have gears to drive just the front wheels, or the front and rear. Chain driven transfer cases use chains to turn one axle in most cases, but can sometimes turn both front and rear. The gear-driven units tend to be stronger and heavier than the chain-driven ones, but the chain-driven ones are lighter, quieter and more compact.
Housings
The two types of housings you might find on a transfer case are married and independent. Married transfer cases are attached to the transmission directly, or in some cases actually sharing the same housing as an integral part of the transmission itself. The independent variety is not attached directly to the transmission. The transmission output shaft is bolted to this type of case, and the case is connected to the differentials on the front and rear by a short drive shaft.
Shift Types
Electronic shift-on-the-fly transfer cases use buttons or a selector switch mounted on the dash board to send messages to the sealed automatic locking hubs on the front axles or drive flanges. The manual shift-on-the-fly uses a lever on the transmission hump and the locking hubs may be sealed automatic hubs or they may have manual lock and unlock selectors on them.
Maintenance
Transfer cases do not need much maintenance, but doing the little bit that is required can prevent future breakdowns. In some cases, the transfer case fluid may need to be periodically replaced. You’ll also want to periodically have the unit inspected for leaks or damage.
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