Every SUV on Illinois freeways has a differential, and it is essential to the proper operation of the vehicle, but most Joliet motorists don’t have a clue what it is.

The differential compensates for differing wheel speeds. For example, when you turn, the inside tire on the turn travels a much shorter distance than the outside wheel. So the inside wheel of the SUV must move at a slower speed than the outside wheel. Without a differential, the wheels would hop and scrape while turning.

Have you ever seen the large bugle-shaped object in the middle of the rear axle of a truck? That’s the differential. In a rear-wheel drive vehicle, the differential is located on the back axle. Four-wheel drive vehicles and SUV’s have differentials on both the front and the rear axle.

You might expect that the differential is located on the front axle of a front-wheel drive vehicle. You’d be right. But the differential is called a transaxle on a front-wheel drive vehicle because its location allows it to be combined with the transmission.

In an all-wheel drive vehicle, an additional differential or transfer case is located between the front and rear axles. Differentials are strong: They have to be because of the important job they do. But those tough parts need proper lubrication. You don’t want your differential to seize up. That results in pricey damage to your SUV.

So you need to have your SUV differential serviced regularly. It’s not a complicated job. At Tuffy Joliet in Joliet we've been servicing differentials for many years. The used lubricating fluid is simply drained and then replaced. Some vehicles require specific additives in the differential fluid; your Joliet service center will ensure you are getting what your SUV needs.

The intervals in time or mileage for servicing your differential vary greatly from vehicle to vehicle. Check with your owner’s manual or Tuffy Joliet to find out how often your SUV differential needs to be serviced.

Generally, however, front-wheel drive vehicles need their differential serviced more often than rear-wheel drive vehicles. Also, if you spend a lot of time off-road or on Joliet area dirt or gravel roads, or if you drive through water, you will need to service your differential more often than the standard recommendation – check with your friendly Tuffy Joliet technician.

Preventive maintenance for your differential is good car care that can spare you expensive repair bills. Knowing what your differential is and how it operates is vital and will help you understand why this is good auto advice. Remember, take care of your SUV, and it will take care of you.