Even the simplest vehicle requires several parts to transmit power from the engine to the wheels. On rear-wheel drive cars and trucks, this system typically involves a component known as a differential. The rear differential transmits rotational power to your vehicle's driven wheel or wheels while also allowing them to spin at different rates.
This function is critical since wheels that turn at the same rate would lead to instability and rapid tire wear when taking turns. Although differentials are relatively simple components, they often need to deal with large amounts of power and can wear out over time. If you drive an aging rear-wheel drive vehicle, it may be time to start listening for the symptoms of a failing rear differential.
Symptoms of a Dying Differential
The interior of a differential consists of several gears and shafts with oil that helps to keep these parts lubricated and cooled. The outer housing of the differential protects its internal parts while keeping the fluid contained. Although every part of a differential experiences wear and tear over its lifetime, the lubricating fluid (or differential oil) generally keeps everything working well.
Unfortunately, numerous external factors can cause your differential to wear down more quickly, ultimately causing it to fail. Common symptoms include a rumbling or howling noise from the vehicle's rear and noticeable driveshaft vibrations. You'll usually hear these sounds from the vehicle's center instead of one of the wheels.
Note that although the initial symptoms of a failing differential may not seem severe, they can rapidly progress. Driving with a faulty differential can cause your tires to wear unevenly, make your vehicle less stable in turns, and ultimately reduce your ability to maintain control.
Common Causes of Differential Failure
If differentials are so durable, why do they fail? The answer usually comes down to poor maintenance or poor usage. Although the differential oil helps to maintain the internal parts, it can wear down over time or become contaminated by tiny flecks of metal produced by wear on the gears. As the fluid loses its lubricating qualities, the gears in the differential will heat up and wear more quickly.
Fluid leaks are another common source of trouble. Since most vehicles cannot monitor differential fluid levels or provide a warning when levels fall too low, it's easy to ignore a small leak. As the internal fluid level drops, the gears will lose lubrication and begin to fail. Parts failures can occur long before the differential runs completely dry.
Fixing a Failing Rear Differential
The good news is that you'll usually have several options for fixing a failing differential. Sometimes, you may only need to replace a seal and restore the fluid to its appropriate level. In other cases, your mechanic may need to pull the differential from the vehicle and perform a full rebuild. Finally, replacing the differential may be necessary when few (or no) internal parts are still worth saving.
For more information, contact an auto repair shop near you.