When you turn a corner in your car, the wheels on the outside of the turn have a slightly longer distance to travel than the inside wheels. That means the outside wheels must rotate faster than the inside. The piece of mechanical wizardry that makes this possible is called the differential.

The differential allows the drive wheels to rotate at different speeds while turning without the wheel binding or hopping. If you have a rear-wheel drive vehicle, the differential is on the rear axle. You may have seen a bulge in the middle of the axle when behind a big truck—that is the differential.

If you have a front-wheel-drive vehicle, the differential function is handled by your transaxle. All-wheel-drive vehicles have differentials on both axles. They also have a center differential or a transfer case between the front and rear axles to compensate for speed differences between the front and rear.

All the power of the engine is transferred through the differentials, so proper lubricating fluid is important to cool and protect the gears. Your service technician can check the differential fluid level and top-off if necessary. With low fluid, the differential will run too hot and wear prematurely. Ask your service advisor for recommendation when to change your differential fluid.

Fresh fluid can extend the life of your differential. We may recommend a high-grade synthetic fluid. Your technician will also inspect the u-joints, which connect your drive shaft to the differential and may recommend service. Some u-joints can be lubricated as part of a routine lube, oil, and filter change.

Differentials eventually wear out and need to be replaced. You might notice a strange noise from the axle as a warning sign. When the differential shows signs of failure, do not delay repair. If repairs are neglected too long, the differential can halt when driving and cause serious hazards from losing control of the vehicle. This can also damage other parts like the axle, driveshaft, and transmission.

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