Signs of Bad or Failing Differential / Gear Oil – Mr Parts ©
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Signs of Bad or Failing Differential / Gear Oil

Posted by Auto Surgeons on

Sometimes the differential begins to show signs of failing (usually in high-mileage vehicles). If you ignore the warning signs, your drive-train could lock up completely, causing you to lose control of the vehicle. Thus, even though it's not a common problem, it's important to pay attention to your car's differential and take the vehicle to a trusted transmission repair shop if you notice any of the signs of failure (which we'll describe below). Often, the mechanic can cure the problem simply by adding differential fluid, but occasionally, more extensive differential repairs need to be made.

Symptoms of a failing or bad differential / gear oil

Modern vehicles use a variety of fluids for the lubrication of their various mechanical components. Since many of the components are made of metal, they require heavy duty oil that is capable of protecting the components from damage due to overheating and metal-to-metal contact. Automotive lubrication fluids play a very important role in the overall performance and service life of a car and can cause components to become seriously damaged when they run low.

One of these types of fluids is the differential oil, also commonly known as gear oil, which is used to lubricate manual transmissions and differentials. Since gear oil is basically the equivalent of what engine oil is to the engine, it plays a very important role in protecting the differential and transmission, allowing them to do their jobs safely and smoothly. When the fluid gets dirty or contaminated it can put the components that it is meant to protect at risk of accelerated wear and even permanent damage. Usually bad or failing differential oil will produce a few symptoms that can alert the driver of a potential problem that should be serviced.

Vehicle has exceeded gear oil service interval

All vehicles come with a maintenance schedule for its fluids and filters that is based on mileage. If the vehicle has exceeded the recommended mileage for service of the gear or differential oil it is highly recommended to have it changed, as old oil may not provide the same level of protection as clean, fresh oil. If the vehicle’s components are ran using old or dirty oil, this may leave them susceptible to accelerated wear or even serious damage. "Prevention is better than cure".

How to tell if the differential is failing

When a differential begins to go bad, it usually starts with mild symptoms that will soon escalate quickly. Since the differential is virtually silent when it's working properly, unusual noises will typically be your first indication of a problem. Here's what to look/listen for, specifically:

  • Whistling noise: If you hear a high-pitched whistle or whine around the axle where the differential sits, this is often the first sign of trouble. (You might have to turn down the radio to hear it.)
  • Rumbles or clunks around the axle: This is a sign that things are getting worse. You may first hear this sound when you accelerate, then more frequently when you're coasting as the problem worsens.
  • Drag on the vehicle: The car may feel more sluggish when you're coasting, especially at low speeds. It might feel like you're driving on low tires.

If you experience any of these symptoms with your vehicle, it's important not to ignore them. If you do, you could experience a dangerous breakdown on the road and cause more extensive damage to the transmission or differential/axle. Take the car to a trusted repair shop to have the differential inspected (and repaired, if necessary).



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(Credit to:  North Seattle Transmission,     - Ed Ruelas)

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  • Please I drive Toyota Corolla 2003

    If I press throttle and release it, unless I match break before pressing the throttle again, the rpm keeps going high while the car drag down instead of it to accelerate

    adesanya oluwatosin on
  • Please I drive Toyota Corolla 2003

    If I press throttle and release it, unless I match break before pressing the throttle again, the rpm keeps going high while the car drag down instead of it to accelerate

    adesanya oluwatosin on
  • Lexus Rx 330, it off when engaged in drive. Starts normally but once I engage in drive, engine stops

    Ajayi Olushina olawale on
  • I never knew that it’s possible that your car’s differential is failing and getting worse if it’s making a sound when you’re accelerating. My husband fetched me last night from a party, and I got annoyed with the rumbling sound of his car that seems to get worse as he drives further. I will make sure to consider finding a differential repair service for his car. Thanks!

    Ellen H. on
  • First things first. Have you tried draining out the CVT fluid and refilling with new oil? Also have the filters changed if possible.

    Admin on

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