Four wheel drive systems allow all four wheels on a vehicle to spin simultaneously. All 4WD vehicles have a transfer case between the front and rear axles that prevents the axles from spinning at different speeds. Rougher terrain can have a heavier impact on the life of your 4WD system. Smooth and consistent four wheel drive system performance is made possible through routine maintenance, which can vary from vehicle to vehicle. Consulting your owner’s manual is extremely important when it comes to scheduling services within proper maintenance intervals. When scheduling 4WD maintenance, consider where you drive most often and how much time your vehicle spends on difficult terrain. Symptoms that show 4WD system repairs are needed include excessive noise while switching between gears, transfer case gear leaks and failures, unusual vibrations, and of course, a warning light on the dashboard.