The pinion seal is made of sturdy material and designed to withstand the heat generated by the differential while you’re driving. But as time passes, the seal can degrade, leading to reduced performance or even outright failure.

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You can also use an inch-pound beam-type torque wrench to measure the drive pinion’s rotating torque. But note that the problem with this method is that you’ll need to remove the brake pads or brake drums while measuring the rotating torque to get a true reading, which should be about 20 inch pounds to keep the pinion rotating. Initially the torque reading may be a bit higher, but see what it is while you’re rotating the pinion.

New pinion seals can go for anywhere between $10 and $80. The price can vary based on brand and your vehicle’s make and model.

The pinion seal is a mechanical seal at the front of the differential at the hub or yoke where the driveshaft connects to the rear end. The pinion drives a ring gear which is bolted to a carrier and within the carrier is a set of gears designed to allow the wheels to rotate at different speeds when the vehicle is making a turn. The pinion seal prevents the differential oil from leaking out.

If you have the right tools and experience in DIY auto repair and maintenance, you can replace a bad pinion seal yourself. Otherwise, bring your vehicle to the nearest trustworthy mechanic.

As the gears and the oil heat up, expanding air needs to be able to escape. If it can’t, oil is pushed out past the pinion seal. Some axle vents will have a rubber hose connected to the vent fitting and the hose will be shaped like a question mark to prevent water from entering the differential through the vent. The one shown in the photo has a metal cap for the same reason. You’ll need to remove the vent to inspect it.

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The pinion seal keeps the entire differential system closed. A bad pinion seal will not only compromise the differential’s performance, it can also cause other parts to wear out faster.

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The differential doesn’t have an oil pump; the gears just spin in the oil, which is contained within the differential case. The oil level is usually supposed to be at the base of the fill hole, but there is no indication of any kind that the differential oil is low other than a visible leak. If a leak is ignored so that the differential oil gets low, the gears and bearings will overheat and fail.

Follow the manufacturer’s recommended maintenance schedule for the driveshaft and differential, if there’s any. Note, however, that most manufacturers do not call for differential oil changes.

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In addition to these steps, here’s a video from Richard McCuistian, ASE Certified Master Automobile Technician, demonstrating the process:

Things have gotten really bad if the differential makes clunking, clicking, or whining sounds while you’re driving. These noises are made by metal-on-metal contact between the gears. Fixing a leak won’t fix bad bearings or gears that have been damaged by lack of lubrication.

This is the most common and easily spotted symptom of a bad pinion seal. When a seal gets too old or damaged to maintain its integrity, lubricant will seep out of the differential and drip on the pavement. Inspect the differential housing and driveshaft for fresh differential oil residue.

Make it a habit to measure your vehicle’s differential fluid level or have it done every other oil change. If there’s no visible leak, the differential level should be fine.

No good can come from waiting until your pinion seal is completely broken before finding a replacement. Get a replacement seal now at CarParts.com.

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Sometimes, a pinion seal can still fail despite careful driving and regular maintenance. When that happens, you should replace the bad seal as soon as possible. Ignoring a faulty pinion seal can lead to issues with other differential parts, which will cost you far more to repair down the line.

Getting your hands on a new pinion seal is easier than ever, and you won’t even have to take one step outside your door. You can use your mobile phone or computer to visit CarParts.com. Use our vehicle selector and input your vehicle’s details, including the exact year, make, model, and engine.

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication. Read our full disclaimer here.

If you have a bad pinion seal, it’s best to stop driving your vehicle until you get it repaired or replaced. Thankfully, you can get a replacement that fits your vehicle with the help of CarParts.com.

Most pinion seals can last between 100,000 and 150,000 miles. But heavy use can increase wear and tear on these seals, which can lead to premature failure.

Normally, differential fluid coats the gears’ metal surfaces. The lubricant prevents direct contact between the differential gears, reducing friction and minimizing wear.

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