Diff-What? Signs That Your Rear Differential Is Checking Out

20 May 2019
 Categories: , Blog


Even if you aren't a car person, it's likely that you are familiar with basic components such as the engine, transmission, and braking system. If you drive a rear-wheel drive or all-wheel drive vehicle, however, there is another component that is nearly as important: your differential. Like your car's transmission, your differential is a gearbox that is responsible for the transmission of power. In the case of the rear differential, it's the final step in the complex process of converting the energy created in your car's engine into power at the rear wheels.

Why Your Car Has a Differential

Although modern differentials are fairly complex pieces of machinery, the basics are simply. At their core, differentials are gears and oil contained within a solid casing. Depending on your particular vehicle, your differential box may be sealed or it may be serviceable so that the gear oil can be changed. Why do you need another box of gears between your engine and your wheels? The key is to understand that your wheels are not always moving at the same speeds. If you picture a car that is moving through a corner, it will be obvious that the inner wheels do not need to travel as far as the outer wheels. Although this small distance might seem insignificant, it is incredibly important for your car's handling and for your tire's longevity that a differential allow each wheel to spin at different speeds.

Note that if your car is front-wheel drive then there is no need for a rear differential or rear axle repair. No power is being transmitted to the rear wheels, so they can spin freely as needed.

Symptoms of Differential Trouble

Differentials are fairly robust, but they can still fail due to neglect, driving issues, or manufacturing defects. Depending on the underlying problem, differential problems can be very obvious or far more subtle. In general, it is worth paying attention to any of the following symptoms:

  • Unusual noises from the rear of the car, especially whining, grinding, or whirring that does not seem to be coming from the wheels
  • Transmission harshness, especially clunking or jerking
  • Unusual tire wear on your rear tires
  • "Sloppiness" in rear handling that does not seem related to your suspension or to worn tires

Unfortunately, many of these symptoms can also be caused by other problems. Since failed or failing differentials can cause serious drivability issues, however, it is important to attempt to diagnose them as quickly as possible. While it can be difficult to determine if the differential is definitely the cause of your problems simply from a test drive, it is usually much easier for professional mechanics to pinpoint the issue with your car raised on a lift.

What to Do About a Failing Differential

If your differential is failing you, it isn't time to give up on your car. While differentials are not cheap, this is generally a much easier and simpler repair than a blown transmission or engine. Depending on the underlying cause of the problem, it may be possible to repair or rebuild your differential rather than replacing it entirely. In fact, it generally takes a lot of effort to completely destroy a differential, so in most cases a complete replacement will not be necessary. Since it usually takes no more than a few hours to remove and replace a differential, labor costs also tend to be more reasonable than with other major jobs.A place like, Huntington Beach Transmissions, can help you learn more.