Don’t be embarrassed if you don’t know what a differential is – you will in a moment. That fact is that if you drive a car, you have a differential. Whether your vehicle is front-wheel drive, rear-wheel drive or four-wheel drive, you have a differential. You might even have two or three.
As you might guess from the name, a differential’s job is to compensate for differences. Specifically the differences in wheel speed when turning. For instance, imagine taking a corner. Your inside wheel has a shorter distance to travel than the outside wheel as you go around the corner. That means that your outside wheel has to turn faster to keep pace with the inside wheel.
The differential allows the wheels to turn at different speeds while still providing power. Without a differential, our tires would scrub and hop along the pavement during turns.
You’ve probably noticed the big bugle in the middle of the rear axle when you’re behind a truck. That’s the differential. Rear-wheel drive vehicles have a differential in back. Most four-wheel drive trucks and SUVs will also have a similar differential on the front axle.
Front-wheel drive vehicles’ differential is called a transaxle because it combines the differential and transmission in one unit. An all-wheel drive vehicle will have a differential or transfer case that adjusts for speed differences between the front and rear drive wheels.
It can seem a little complicated. But you can see that all of the engine’s power is routed through your differentials. They’re strong enough to handle the work, but they need to be properly lubricated in order to stay strong. So from time to time, you need to have your differential serviced. The used fluid is drained and replaced with clean fluid. Some differentials also require special additives to be installed.
The rule of thumb for the time and mileage interval for servicing your differential, can vary greatly by vehicle. A front-wheel drive vehicle’s transaxle will need servicing more frequently than the rear differential on a pick-up truck, so check with your service adviser or your owner’s manual for recommendations.
How and where you drive will have an impact as well. If you drive on dirt roads or through streams, you’ll need to service the differential much sooner than if you always stay on the pavement.