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Does your differential mount need to be replaced? You might not think about it often, but it’s crucial to both the comfort and the safety of your daily driving experience. By supporting the differential in place, it cushions the car from vibrations on the road and also positions the component so that it plays nicely with other crucial driveline pieces, such as driveshafts, transmissions and axles.

These three signs will let you know if it’s time to replace it.

Continuous Shaking

The most obvious sign that your differential mount needs to be replaced is a gradual increase in the level of vibration that you feel inside the cabin. Once the rubber or polyurethane material on a differential mount begins to wear, it becomes less effective at holding the differential in place. Over time, the differential can begin to move in relation to the inputs it receives from the driveline.

This often manifests as a shudder or shake when the vehicle is accelerating, but it can occur over such a long period of time that you eventually adjust to the fact that you no longer have a smooth ride — right up to the point where the mount disintegrates and begins shaking and chattering much more aggressively. It may also only be noticeable at certain speeds, so keep that in mind when hunting down a driveline shake.


Once a differential mount loses its tight hold, the diff itself will begin to interact with rest of the driveline in ways that are out of the ordinary. One of the most common manifestations of this newfound freedom of movement is a “clunk” that is typically heard at the initial moment of acceleration, as well as when lifting off of the gas pedal to decelerate. If you have a car with a manual transmission, you could hear this clunk when shifting gears.

What you’re hearing is the sound of the differential moving as it goes from “loaded” to “unloaded” under acceleration and immediately after coming off of the gas pedal, in terms of driveline stress. Since the mount’s cushioning has degraded, it’s making contact with other parts of the chassis or it could be moving in relation to the driveshaft or the vehicle axles, with the resulting noise coming from the joints.

Puddles Underneath the Car

If your differential mount has been shaking and clunking long enough, it might have undergone enough stress to begin leaking out of its seals. A puddle of fluid underneath your diff is a sign that something is wrong back there and that it’s time to inspect the mount, the axles and the driveshaft. A loose differential can also potentially have an impact on a transmission’s output shaft seal if it pulls and tugs hard enough for long enough. Therefore, any fluid pooling near the gearbox — in combination with the other symptoms discussed here — could also be linked to a bad mount.

Don’t put off inspecting and replacing this component if you notice these three signs with your car. You’ll end up saving yourself further potential driveline damage down the road and gain a much smoother ride to boot.

Check out all the driveline parts available on NAPA Online or trust one of our 16,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on your vehicle’s differential mount, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

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