How to Replace Rear Main Seal Chevy 350

The process of installing a new main seal for your Chevy 350 may seem challenging, but it’s straightforward.

Do you know how to replace the rear main seal Chevy 350?

Chevy 350’s rear main seal protects the engine oil. It sits between the crankshaft’s outlet extension and the engine block.

When the vehicle moves fast, it vibrates. These vibrations usually damage a car’s rear main seal.

Also, the heat produced by the Chevy 350’s engine affects the seal. You can have the seal replaced by an expert, but it takes time and much of your hard-earned dollars.

Fortunately, the process is an excellent DIY home project. You can do it to save time and money.

Follow the following simple steps by steps, and you shall know what to do when your Chevy 350’s primary rear seal gets damaged.

A Step by Step Guide on How to Replace Rear Main Seal Chevy 350

You can remove the transmission or allow it to stay while replacing the seal. But the process which involves transmission removal is daunting and complicated.

The simple method is to replace a rear main seal without removing the transmission, as illustrated in this guide.

Step 1: Collecta the Necessary Tools

The process entails the removal of various parts of your Chevy 350 to reach the rear main seal. You will require the assistance of some tools to do so. Before you start anything, ensure you collect the following;

  • Wrench
  • Screwdriver
  • Safety gloves
  • A new rear main seal

Step 2: Disconnect the Chevy 350’s Battery

While dealing with tools and heavy machines, accidents are bound to happen. It’s essential to take safety precautions. Before doing anything, put on your safety gloves to protect your hands.

For safety reasons, it’s vital to remove your vehicle’s battery. But it would be best if you were extra careful since you haven’t removed your Chevy 350’s transmission.

Begin by disconnecting the positive and negative terminals, then take out the battery.

You will have created ample space for carrying out the process.

Before continuing with the next step, keep in mind that you need to note every part you remove and its exact position.

To help you return the parts effortlessly and correctly after installing a new rear main seal, arrange them following each other.

If you doubt your memory, you may take picks of the parts in place and when you remove them. It will help you remember how they were in their locations.

Step 3: Extract the Driveshaft

It would help if you were sensitive in this stage of removing the rear main steel Chevy 350 because the transmission is still intact.

Be alert to avoid accidents and damages. You should remove the driveshaft to create more space and access the Flex Plate.

Step 4: Unfasten the Flex Plate

After accessing the Flex Plate, you need to remove it to give way to the seal’s location. Use a wrench to unscrew it.

Then take it out using a screwdriver. The Flex Plate’s tie may be solid and hard to break. Use any necessary tool to loosen or break it.

You cannot reach the rear main seal without untying the Flex Plate. After taking it out, the rear main seal’s back becomes visible.

Step 5: Take Out the Seal

So far, you have removed various parts to give way to the rear main seal. It means that you are already halfway through the Chevy 350 rear main seal replacement process.

With the seal being visible, it’s time to remove it. You will need to put in all your energy to take it out.

Usually, the seal comes pressed on the vehicle’s engine block. It gets pushed on the engine using blots.

First, the seal goes inside the hood, then enters the engine block when pressed. It explains why you require massive energy. The removal process begins with the seal’s hood.

The seal hood contains approximately 6 – 10 bolts. Start by removing the bolts using a screwdriver. Then pull out the hood’s seal.

Note that the aluminum material used to make the hood is fragile. You, therefore, need to handle it carefully as it can easily crack or dent. Remove it slowly and gently.

Step 6: Disconnect the Crankshaft Seal

When you remove the rear main seal’s hood, the seal may come out with it. It depends on your car’s object placement.

If the seal doesn’t come out with the hood, you need to place your hands on it. It means that the rear main seal has stuck in the crankshaft.

You, therefore, need to start poking the crankshaft until it separates. Then take out the seal.

Step 7: Install the New Rear Main Seal

After removing the old one, the new rear main seal is in its place. Going through the instructions manual may help, though it’s easy. Ensure it lies to its exact position.

Step 8: Put Back Other Parts

Remember what we said in the first step when we started removing the parts.

You should have been arranging them in the sequence they follow as you remove them. Start by replacing what you removed last before removing the rear main seal.

Then replace the next part until you put back the battery and reconnect its terminals. If you took a video or some photos, use them to confirm you’re doing the right thing.

When through, you will have successfully replaced your Chevy 350’s rear main seal.

As illustrated in the above guide, changing the Chevy 350 rear main seal is not hard but takes some time.

You, therefore, need to be patient. Don’t carry out the process when in a hurry. The best time is when free.

As a Chevy 350 owner, you may wonder whether replacing its rear main seal is essential. Here is the answer;

Why Replacing the Rear Main Seal is Important?

Your Chevy 350 is useless without a rear main seal. The vehicle’s crankshaft exits the engine case with the help of the rear main seal.

It then bolts to the FlexPlate or flywheel and transfers energy into the vehicle’s transmission.

The car’s engine oil also stays within the engine because the rear main seal holds it securely. As a result, the main bearings remain lubricated.

When the rear main seal cracks, leaks, or gets damaged, it means many problems for your Chevy 350.

The vehicle’s transmission and head gaskets get destroyed. The cost, energy, and time involved in rebuilding the transmission and replacing the head gaskets and the rear main seal is enormous.

That is why it’s crucial to inspect your Chevy 350 for any leaks frequently. If you discover oil dripping from the rear main seal, find the opening and seal it immediately.

Fortunately, the market has numerous top-notch sealants that work like magic in sealing rear main seals. You can easily find one in an auto part store next door.

An excellent example is the BlueDevil Rear Main Sealer. You only need to add it to your Chevy 350’s engine oil, and it will stop the leak.


A rear main seal is essential in any Chevy 350. As discussed above, it helps seal the engine oil inside the engine, keeping the parts well lubricated. In return, the crankshaft meets the transmission effortlessly.

Unfortunately, the rear main seal does not last forever. As explained above, it may get affected by your car’s vibration or engine heat.

When you find black puddles where you had parked your Chevy 350, it is an excellent sign that its rear main seal has a problem.