Replacing A Pinion Seal – A Detailed Guideline

Replacing a pinion seal is a thing you should consider doing quickly in the near future, as it can lead to serious damage to your vehicle engine, such as oil spraying all over the engine.

Even some drivers need to tow their cars due to this reason.

Let’s find out more about the issue and how to replace the differential seal properly!

About The Pinion Seals

Replacing A Pinion Seal

What Is It?

The pinion seals are round mechanical parts that surround the pinion shaft. They can be made from plastic, metal, or rubber. Each type of material has its pros and cons.

The pinion seal location is where the shaft and the differential meet each other.

It is mainly in charge of preventing the leakage of oil or other fluid from the shaft or the axle and blocking contaminants such as dirt from getting inside the differential.

The detail plays an important role in the drivetrain, and you should replace the pinion seal when there’s a leakage.

How Does It Work?

When the drive shaft turns the shaft, the rear diff pinion seal combines with an oil slinger – a small disc in front of the seal to prevent the oil from leaking from the differential housing.

As the part “wraps” the shaft, inside the differential are the small lips of the seal, making the oil that could pass the oil slinger slide up but not under.

The oil then flows back to the differential case, and there’s no liquid between the shafts and the seals.

However, the process doesn’t work perfectly 100%, especially when you have driven your car for thousands of miles.

Thus, in some vehicles, rear pinion seal replacement or front pinion seal replacement is normal and doesn’t mean something terrible as long as you do it immediately after spotting the seepage.

What Are The Reasons For The Seal Leak?

Wear and tear, polluted fluid, hot weather, wrong installation, wrong seals, and the broken differential are the sources of the leak.

Below are some common reasons that lead to the leakage. Let’s follow along for more details!

Wear And Tear

The most common one is the wear and tear of the part. It can become dry, cracked, damaged, and can’t work properly.

Contaminated Fluid

Dirty differential fluid is the second cause you can think of. The dirt and debris circling with the fluid inside the engine’s components create stress on the seals and joints, thus developing seepage.

Hot Weather

A hot climate usually causes the fluid to break down fast. It degrades even quicker if there’s dirt and debris.

The broken-down fluid loses its lubrication, making the joints and seals wear off and causing leakage.

Incorrect Installation

You will see the fluid leak if the detail is not properly sealed. You should position it correctly and apply appropriate pressure to have proper working seals.

Wrong Seals

Before installing, make sure you choose the seals that match the differentials. Consider its size, shape, and materials to prevent fluid from leaking.

Broken Differential

A damaged differential likely dislodges the seals, and a leak can be the consequence (especially a rear differential pinion seal leak).

Following the leak, you might hear a humming noise getting louder with speed.

Replacing A Pinion Seal With 8 Detailed Steps

What Tools Do You Need?

Prepare all these tools below for a safe and proper replacement task. Or else, it’s best to turn to the help of a qualified mechanic.

  • Ball peen hammer
  • ½ Breaker bar – 24 inch
  • Brake cleaner
  • Drain pan
  • Gear oil
  • Jack and jack stands
  • Mallet/plastic hammer
  • Metric wrench set
  • Paint marker
  • A set of puller
  • Pinion seal
  • Repair Manual – For torque specifications
  • ½ Ratchet – minimum length: 18 inches
  • ⅜ Ratchet
  • RTV Silicone
  • Seal puller
  • ⅜ and ½Socket set – Metric and Standard
  • Shop towels
  • ½ socket for pinion nut 
  • Wheel Chocks
  • Wrench set

How To Replace Pinion Seal?

Step 1: Secure Your Car

Park your car on flat ground. Secure the front and rear of your front wheels so your vehicle will not move forwards or backward during the process.

Then, raise the axle to a comfortable height for you to work underneath. Firmly place the jack stands under the axle.

Step 2: Take Out The Driveline

Use the parking brake to ensure your vehicle is stable on all axles. It will help the process go smoothly.

Next, before separating the driveline from the yoke/flange, you should secure it with a strap or bungee, so it will not fall on you.

Take out the driveline mounting bolts connecting the driveline and the axle.

Take a plastic or mallet hammer to hit the end of the driveline to separate it from the flange. You can choose to tie it up so it will not bother your way or totally remove it from the transmission.

You will need a drain pan if you wish to remove it completely. Place it under the end of the transmission so the fluid can drop into the drain pan when you slide out the driveline.

Step 3: Remove The Axle Flange

Make reference marks of the seal and flange’s position with a paint pen. Count the number of exposed threads and write it down.

Thus, you can apply the correct amount of torque without being overtightened.

Remove the yoke/ flange mounting nut. Then place a puller to remove the flange. The securely installed puller helps evenly pull the part out of the pinion.

To do it, you should ensure the driving shaft of the puller is in the center, and there’s a solid square edge for the puller’s arms to pull on.

Once the puller is settled properly, gradually tighten the drive shaft to start pulling the flange off the pinion shaft. Continue and stop driving the center shaft when you see the flange comes off.

Step 4: Remove The Seal

Before removing the component, remember to put a drain pan under the area.

Start the process by using a puller to hook and pry the seal from the inside to remove it. You may need to repeat the step in different placements until you finish the job.

After removing the component, free the inside of the mounts from grime and dirt, and prepare a cleaned surface for the new one.

Step 5: Place New Pinion Seal

Spread a thin layer of RTV silicone on the new detail’s surface and place it against the axle housing.

When you complete positioning, tap in a cross pattern on the edge of the component so it can be installed evenly without damage.

Continue tapping on it until it’s flush with the axle housing. Inspect one more time to make sure everything sits in its place.

Step 6: Install The Axle Flange

Apply a thin layer of RTV silicone to the inside and the surface of the flange that contacts the seals. Install the flange according to the marks made in step 3.

After that, use the mallet to seat the detail enough to have the nut and washer started. Place the grease on the flat washer, tighten the nut, and put these two details into the pinion.

Next, tighten the pinion nut. Make sure you pay attention to the reference marks at every turn.

Plus, don’t miss counting the threads coming out of the shaft’s end.

Once it reaches the desired number, your reference marks should be lined up. If they are not, slightly tighten the nut more for them to match.

Step 7: Put Back The Driveline

If you just secured the driveline up earlier, simply release it. When you remove the part, reinsert it carefully.

Next, lift the driveline and line it up before mounting it to the flange.

Feel free to adjust and mount as the detail slides back and forth in the transmission. Then, mount and tighten the bolts to specification.

Step 8: Check The Fluid Level

The last step is to use your finger to inspect the fluid level, which ideally should be just lower than the fill hole. Add the axle fluid needed if required.

Raise your car, take the jack stands away, release the parking brake, and the process of pinion seal replacement has been completed.


Is Driving With Leaky Pinion Seals Safe?

No. You should know that if you keep driving with your leaking pinion seals, the entire differential fluid will eventually empty, causing damage to your car engine.

It may result in power loss, fuel economy decrease, and even car overheating. So if you see any leakage, repair it as soon as possible to avoid costly damage.

How Much Does The Replacement Cost?

The cost of differential seal replacement varies depending on your vehicle’s model and the leak’s severity.

If the mechanics analyze it’s a serious problem, you may need to replace the entire differential. In most cases, you’ll likely need to pay $200 – $300.


Replacing A Pinion Seal With 8 Detailed Steps

Pinion seals are vital components to keep the fluid inside the differential.

Therefore, replacing a pinion seal is necessary to fix the problem of a leaking pinion seal; otherwise, you may face serious damage to your engine.

Don’t linger on the issue, and follow our instructions above to have the matter addressed.

If you feel it’s hard to handle, there’s nothing wrong with bringing your vehicle to the repair shop for proper fixation.

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