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You can think of a four-wheel drive transfer case as though it were a two-speed transmission with an extra output. Engine power normally goes through high range (or second gear if you think of it as a transmission) in a 1-to-1 ratio. Low range is the transfer cases "first" gear. Power normally flows directly through these gears and out the back of the transfer case, but shifting it to 4WD engages a clutch that s engine power to a second shaft that drives the front wheels as well.
Shifting the Transfer Case
Step 1
Start out with the transfer cases gear selector in the "2WD High" position. This is your standard driving position.
Step 2
Shift to "4WD High". Many older transfer cases require that the vehicle be at a complete stop when engaging 4WD. However, newer "four on the fly" transfer cases generally allow you to engage all four wheels at any speed.
Stop the vehicle and shift into "4WD Low" when you need to overcome obstacles on the trail or pull a heavy load at low speeds. Many transfer cases offer a gear reduction of between 3- and 4-to-1. Youll have about three to four times the power, but that extra grunt comes at the expense of a very limited top speed: about 20 to 30 mph in most cases.
Tip
- Many older vehicles have manual locking hubs, which allow the driver to completely disengage the front wheels from the axle during normal driving to for better fuel mileage. Manual locking hubs typically offer less rotational drag than the automatic locking hubs used on most modern 4X4s, but having them means youll have to stop the vehicle, get out and engage the hubs before using 4WD. You can drive with the hubs locked all the time, but it will kill your gas mileage and put unneeded wear and tear on your differential gears.
