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.
What Is a Pinion Seal?
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.
Bad Pinion Seal Symptoms
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.
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.
Here are some of the most common symptoms of a faulty pinion seal that you should look out for:
Differential fluid leak
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.
Low differential fluid level
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.
Differential makes noises while driving
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.
Normally, differential fluid coats the gears’ metal surfaces. The lubricant prevents direct contact between the differential gears, reducing friction and minimizing wear.
How to Maintain the Pinion Seals
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.
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.
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.
If you drive hard with your vehicle, you should follow an accelerated maintenance schedule.
How to Fix a Pinion Seal
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.
Follow these steps to replace a bad pinion seal:
- Remove the rear wheels and brake drums to expose the differential and its pinion seal.
- Remove the drive pinion nut and pinion flange to access the seal.
- Never use an air impact wrench on the drive pinion nut because this can damage the nut. The nut should be replaced, but you can apply some blue Loctite and reuse the old nut.
- Mark the pinion nut, the socket, and the pinion with correction fluid. axle
- Once you’ve put the replacement pinion seal in place, tighten the pinion nut to its previous position.
- Always check the axle vent to make sure it isn’t clogged. Remove the vent and shine a light through the vent’s orifice to make sure it’s clear. The orifice in the vent fitting is usually just a bit smaller than ⅛ inch in diameter.
- Turn the nut 1/16 inch (1.5 mm) farther than its previous position to ensure that the collapsible spacer (also known as a crush sleeve) can maintain the proper preload on the pinion bearing. If you overtighten the nut, the crush sleeve will need to be replaced, so be careful not to do that.
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.
- Once you’ve installed the new pinion shaft seal, tighten the drive pinion nut. Stop once the rotating torque shows a reading that is 3 to 5 in-lb higher than the reading taken before removing the pinion nut.
In addition to these steps, here’s a video from Richard McCuistian, ASE Certified Master Automobile Technician, demonstrating the process:
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.
How Much Does a Replacement Pinion Seal Cost?
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.
Finding a Replacement Pinion Seal For Your Ride
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.
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.
We make it a point to get our auto parts from some of the most trusted manufacturers in the industry. On top of that, our warehouses are located all over the US, meaning you can receive your order within days.
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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