Four-wheel drive vehicles are designed for driving situations where all four wheels need to be engaged. You can check to be sure your system is operating properly. It is best to test your 4-wheel drive system on a flat surface.
Step 1 - Check for Unusual Sounds
Engage your 4-wheel drive system. Shift your gear shift in order for the vehicle to move ahead. Listen carefully for any abnormal sounds or vibrations. If there are no unusual sounds, your vehicle has passed the first check point.
Step 2 - Increase the Vehicle Speed
Increase to a low rate of speed of your vehicle. Check to see whether the RPMs increase while the vehicle is moving slowly. If they rise quickly, the gears of the transfer case of your 4-wheel drive are operating properly. Your vehicle has passed the second checkpoint.
Step 3 - Drive in a 4-Wheel Situation
Drive your vehicle in a situation that requires the use of your 4-wheel system. If there is any mud or steep, hilly areas nearby, drive your vehicle through them. Your front tires should be attempting to gain traction on the surface. If the front tires are rotating somewhat faster but the vehicle speed remains constant, your vehicle has passed the third test.