How to Fix a Differential Leak

Differential leakA differential leak is not an uncommon leak on many vehicles equipped with a differential.  But how do you know if your vehicle has a differential?  It used to be as easy as saying that if you drive a truck or SUV your vehicle has one, and if not, your vehicle doesn’t but today’s advanced engines and drivetrains, it’s best to take a peek under your vehicle and identify the differential before diagnosing the problem.

The differential in your vehicle accomplishes a variety of tasks all in a small space.  The main purpose of the differential in your vehicle is to multiply the power transmission devices.  Your vehicle has just one engine but must drive 2 or 4 wheels with that engine.  For vehicles that are front wheel drive, the multiplication happens inside the transmission, which can technically be called a transaxle.  A transaxle takes one input from the engine and turns it into 2 outputs, one to each of your front wheels.

In the case of a 2-wheel drive vehicle that is rear wheel drive, power exits the transmission through the driveshaft and the driveshaft provides a single input into a differential.  Inside the differential that single power input is split into two shafts, the axles, to supply power to both rear wheels.  If your vehicle is 4-wheel drive, then you’ll have a transfer case after the transmission that splits power into a front and rear driveshaft which each supply power to their own differential.

The differential in your vehicle also provides another important drivetrain feature and that is providing the final drive ratio.  Even with the gear reduction in your transmission, the driveshafts in your vehicle are spinning very quickly so you need one final gear reduction to reduce the speed.  Differentials can reduce the driveshaft speed by half, ¾ or even up to 1/6 of the speed!

The speed reduction and shaft multiplication that happens in your differential requires a specific type and set of gears to correctly change the shaft speed, multiply it into 2 outputs and don’t forget, transfer the power at a right angle!  This requires a ring gear, pinion gear, spider gears and carriers to support them.

This set of gears requires specific types of lubricants to make sure things stay cool during normal operation and that wear is kept to a minimum.  Along with the gear set, very specific bearings are used to carry the loads on the shaft and keep the gears at exact distances from each other so the gear teeth can engage properly.  Like any lubrication, there are seals to keep the lubricants from running out of your differential.  Some differentials put these seals just outside the bearings, while others have the seals all the way at the end of the axle tube.  Due to different designs, your differential can leak from many different places making it difficult to determine the exact leak location.

Rather than searching for where your leak is coming from, simply add BlueDevil Oil Stop Leak to your differential oil through the oil fill plug and your leaking seal will be reconditioned and restored while you drive!

For more information about BlueDevil Oil Stop Leak and how to seal your differential leak, click on the banner below!
BlueDevil Oil Stop Leak






You can purchase BlueDevil Oil Stop Leak at any of our partnering local auto parts stores like:

  • AutoZone
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Pictures Provided By:

differntial_leak.jpg – By Loraks – Licensed by Getty Images – Original Link

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8 responses to “How to Fix a Differential Leak

    1. Jerry-

      No, the product does not harden or thicken in any way, so it would not cause any adverse affects in the system. Feel free to contact our technical support office at 888-863-0426 with any other questions.

      Thank you!


  1. Have very slow axle seal leak on rear differential on a 2013 Toyota Tundra. In fact leak must of just started because pulling off passenger side disc caliper to adjust emergency brake shoes noticed emergency brake shoes were damp with rear end grease but not dripping out of emergency brake drum. Question is will this product help & how should I use it far as how much compared to the amt of diff. fluid in diff. Also will it be compatiable with the synthtic fluid Toyota put into it 10,000 miles ago.
    Thanks, William Pullen

    1. William-

      Thank you for asking about your Toyota Tundra. Based on your description, we recommend using the BlueDevil Oil Stop Leak ( You will be using one oz. of the product per quart of fluid in the system. Yes, the product is compatible with synthetic differential fluid. You should expect to see results after approximately 100-200 miles of driving.

      Thank you!


        1. Adam-

          For a rear differential leak, we recommend using the BlueDevil Oil Stop Leak. BlueDevil Oil Stop Leak is more concentrated and is the universal application that will work for various leaks such as oil pan leaks, rear main leaks, valve cover gasket leaks, etc. Whereas the Rear Main Sealer is specifically formulated for only a leaking rear main seal. If you are not 100% sure where the vehicle is leaking or there seem to be multiple leaks then we recommend using BlueDevil Oil Stop Leak. You should expect to see results after approximately 100 miles of driving.

          Thank you!


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