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Replacing Your Vehicle’s Rear Main Seal: A How-To Guide




The rear main seal is an important component of a vehicle’s engine. It is responsible for preventing oil leaks from the back of the crankshaft, which could lead to engine damage or failure if left unchecked. Over time, the rear main seal can become worn or damaged due to normal wear and tear, high mileage, or other factors.

Replacing a rear main seal can be a complex and time-consuming process that requires specialized tools and knowledge. However, it is essential for maintaining the health and longevity of your engine. In this article, we will discuss everything you need to know about rear main seal replacement, including when it should be done, how it’s done, and what to expect during the process.

Before we dive into the details of replacing a rear main seal, let’s first take a closer look at what this component does and why it’s so important for your vehicle’s performance. Understanding how your car works is crucial in taking care of its parts and avoiding untimely repairs.

Overall, proper maintenance will save you money in the long run by extending your car’s lifespan while reducing risks associated with unforeseen damages caused by lack thereof adequate care for your car’s components such as its rear-main-seal.

Symptoms of a Faulty Rear Main Seal

The rear main seal is an essential component of the engine that helps to prevent oil from leaking out. When it starts to fail, it can cause a range of problems for your vehicle. Here are some common symptoms to watch out for:

1. Oil leaks

One of the most obvious signs of a faulty rear main seal is oil leaks. You may notice spots on your driveway or garage floor where your car has been parked, or you might see smoke coming from under the hood as the oil drips onto hot engine components.

2. Low oil pressure

A faulty rear main seal can also cause low oil pressure in your engine. This can happen because the seal isn’t doing its job properly and allowing oil to leak out, which means there’s less lubrication for vital engine parts.

3. Engine noise

If you hear strange noises coming from under the hood, such as knocking or tapping sounds, this could be another indication that there’s something wrong with your rear main seal. This is because low oil pressure can cause increased friction between moving parts in the engine.

4. Poor acceleration

Another symptom of a failing rear main seal is poor acceleration performance. This happens because low oil pressure means that certain parts of your engine aren’t getting enough lubrication and therefore aren’t working at their full potential.

5. Smoky exhaust

Finally, if you notice smoky exhaust coming from your car’s tailpipe, this could be due to a faulty rear main seal causing excess oil consumption and burning inside the combustion chamber.

If you experience any of these symptoms while driving, it’s essential to get them checked by a mechanic as soon as possible before they worsen and potentially lead to more significant issues.

Tools and Materials Needed

Replacing the rear main seal is a job that requires several tools and materials to be done efficiently. Here are the essential items you need to gather before starting the process:


  • Ratchet and socket set: You will need sockets of different sizes, ranging from 8mm to 19mm, depending on your car model.
  • Torque wrench: A torque wrench is essential in tightening bolts and nuts with accurate torque specifications.
  • Screwdrivers: Both flathead and Phillips screwdrivers come in handy when removing bolts or screws from various parts of your engine.
  • Pry bar: You may need a pry bar to remove some stuck parts such as pulleys or covers gently.
  • Gasket scraper/razor blade: These tools come in handy when scraping off old gasket material from surfaces without damaging them.
  • Seal installer/remover tool kit: These kits include various sized sleeves, handles, adapters, or plates used for installing new seals accurately without damage.


  • New Rear Main Seal: Ensure that you buy a high-quality seal that fits perfectly with your car model.

  • New Oil Filter: It’s advisable to change the oil filter since it can get contaminated during the repair process.

  • New Engine Oil: Always use fresh engine oil after replacing the rear main seal since some oil might have leaked out during repairs.
  • Gasket Maker/RTV Silicone Sealant: This helps create an effective seal between two surfaces where there was no gasket before such as valve covers.
  • Clean Rags: You will need several clean rags to wipe off oil spills or debris from the engine parts.
  • Brake Cleaner/Engine Degreaser: Use these solvents to remove grease, dirt, and grime from surfaces that come into contact with the new seal.

In conclusion, having all the tools and materials listed above is essential for a successful rear main seal replacement job. Ensure that you have gathered everything before starting since any missing tool can cause delays or damage during repairs.

Preparing Your Vehicle

Before you begin the process of replacing your rear main seal, it is important to properly prepare your vehicle. Here are some steps to follow:

Gather Necessary Tools and Supplies

Make sure you have all the necessary tools and supplies before beginning the job. This may include a socket set, torque wrench, oil filter wrench, gasket scraper, seal installation tool, RTV silicone sealer, new rear main seal and oil filter.

Drain Oil

Drain the engine oil from your vehicle by removing the drain plug located on the bottom of your engine’s oil pan. Allow all of the old oil to fully drain out before proceeding.

Remove Transmission or Engine

Depending on your make and model of vehicle, you may need to remove either the transmission or engine in order to access and replace the rear main seal. Consult your owner’s manual or a trusted mechanic for guidance.

Clean Surfaces

Clean any surfaces that will come into contact with new seals or gaskets thoroughly with a gasket scraper. Make sure there is no debris left on these surfaces before installing new parts.

Install New Seal Properly

When installing a new rear main seal be sure that it is inserted evenly into its housing using an appropriate installation tool (if required). Apply a small amount of RTV silicone sealer around any areas where leaks could occur such as bolt holes or mating surfaces.

By following these preparation steps carefully, you can ensure that replacing your rear main seal goes smoothly without any issues along way.

Removing the Transmission

Before you can replace the rear main seal, you will need to remove the transmission. This may seem daunting, but with proper preparation and tools, it can be done relatively easily.

The first step is to disconnect the battery and remove any electrical connections from the transmission. Next, drain all of the fluid from the transmission and transfer case (if equipped). Once drained, remove any linkage or cables that connect to the shifter or transfer case shift lever.

Next, support the engine with a jack stand or engine hoist so that it does not fall once you remove its support bracket. You will also need to loosen any bolts connecting exhaust pipes or driveshafts to allow for movement during removal.

You should now have access to all of the bolts connecting your transmission to your engine block. Use a socket wrench and extension bar combination along with an impact gun if necessary, as some bolts may be stubbornly tight. Once all bolts are removed, gently lower your transmission down using a jack stand until it clears your car’s bodywork.

If you’re having difficulty removing your transmission due to rusted or corroded parts in older vehicles, consider using penetrating oil on such parts before attempting removal again; this will help lubricate them enough for easier separation without damaging anything else nearby in their path.

In summary: removing a vehicle’s transmission is no easy feat but is essential when replacing its rear main seal since you’ll need full access behind it where this component resides entirely out-of-sight unless disassembled fully beforehand! Take care during each step outlined above while wearing appropriate safety gear like gloves and eye protection throughout every stage of disassembly/assembly process involved here too!

Accessing and Removing the Old Seal

To access and remove the old rear main seal, you will need to follow a few steps. First, you will need to disconnect the negative battery cable to ensure safety while working on your vehicle.

Next, you will need to drain the engine oil from your vehicle’s crankcase. This can be done by removing the oil pan drain plug or using an oil extractor tool. Once all of the oil has been drained out of the engine, you can move on to removing other components that may be blocking access to the rear main seal.

Depending on your specific make and model of vehicle, there may be additional parts that need to be removed before accessing the rear main seal. For example, some vehicles require removal of transmission crossmembers or exhaust systems in order to gain clearance for removal of the seal.

Once all necessary components have been removed, you can begin removing any bolts or clips holding in place around your old seal using specialized tools such as pry bars or screwdrivers designed for this purpose. Carefully work around each edge until it comes free from its housing without damaging any surrounding parts like gaskets or seals nearby that may also require replacement during this process.

When installing new seals into their respective locations after removals are completed safely with proper torque specifications followed closely so they don’t leak later down road!

Installing the New Seal

Now that you have removed the old rear main seal, it’s time to install the new one. Here are the steps you need to follow:

1. Clean the surface: Before installing the new seal, clean the surface where it will be installed thoroughly. Use a cleaning solvent and make sure there is no debris or oil on it.

2. Apply lubricant: Apply some lubricant to both sides of the new seal before installation. This will help it slide into place more easily and reduce friction.

3. Install the seal: Carefully press the new seal into place, making sure it is centered in its housing and flush with its mating surface.

4. Use a tool: You can use a special tool designed for this purpose or improvise with something like a socket or block of wood to tap gently around its circumference until fully seated.

5. Check for proper fitment: Once you’ve installed your new rear main seal, take some time to inspect everything closely and ensure that there are no leaks or other issues.

6. Reassemble components: Finally, reassemble all of your components in reverse order from how they were taken apart earlier in this process so that everything is back together correctly again!

By following these steps carefully, you should be able to replace your rear main seal without any problems whatsoever!

Reassembling Your Vehicle

After successfully replacing the rear main seal, it is time to reassemble your vehicle. Here are the steps you need to follow:

1. Replace the oil pan gasket: If you removed the oil pan during the process of replacing the rear main seal, make sure to replace its gasket before installing it back onto your vehicle.

2. Reinstall any parts that were removed: This includes reinstalling any brackets or components that were removed in order to access and replace the rear main seal.

3. Install new transmission fluid: Before installing your transmission back into place, make sure to add fresh transmission fluid as per manufacturer’s recommendations.

4. Reattach driveshaft and exhaust system: Once everything else has been installed, reconnect both driveshaft and exhaust system securely in their respective places.

5. Refill engine with oil: Add fresh engine oil as recommended by the manufacturer using a funnel inserted into your engine’s oil fill hole.

6. Start up your vehicle for test drive: After making sure all bolts have been tightened down properly and no leaks are present, start up your vehicle for a test drive around town at low speeds before heading out on longer trips.

By following these steps carefully, you can ensure that everything is put back together correctly after replacing a faulty rear main seal on your vehicle’s engine!

Testing Your Vehicle

Before hitting the road after replacing your rear main seal, it is important to test your vehicle for any leaks or issues. Here are some steps you can follow to ensure that your car is in good condition:

Step 1: Check the Oil Level

Start by checking the oil level in your car. Make sure that the oil level is not too low or too high. If there are any discrepancies, add or remove oil as needed.

Step 2: Inspect for Leaks

Inspect the area around where you replaced the rear main seal for any signs of leaks. Look for wet spots or puddles under your car and check if there are any drips on the ground.

Step 3: Take a Short Drive

Take a short drive around your neighborhood and listen carefully to how your engine sounds. Pay attention to any unusual noises such as knocking, ticking, or grinding sounds.


  • Avoid driving at high speeds during this initial testing phase.
  • If possible, try driving on different types of roads such as highways and back roads.
  • Park your car on a clean piece of cardboard overnight to help detect small leaks.

Step 4: Recheck Oil Level and Inspect Again After Driving

After taking a short drive, recheck the oil level in your car and inspect again for leaks. If everything seems fine, take another longer drive before rechecking once more.

By following these steps and taking precautions while testing out new repairs made to their vehicles will enable drivers with peace of mind knowing they have done everything they could do make sure their vehicle is safe on all fronts when getting back behind its wheel!


Replacing a rear main seal is not an easy task, but it can be done with the right tools and knowledge. The first step is to identify the symptoms of a worn-out rear main seal, which includes oil leaks from the back of the engine, low oil pressure, and excessive oil consumption.

Once you have identified these symptoms, you need to remove the transmission or transfer case to access the rear main seal. This process requires special tools such as a puller and installer tool kit.

It is important to note that replacing a rear main seal requires attention to detail and patience. You must ensure that all parts are cleaned thoroughly before installation and correctly aligned during assembly.

If you are not comfortable performing this repair yourself or do not have access to the necessary tools, it is best to take your vehicle to a professional mechanic. They will have experience in replacing this type of seal and can ensure that everything is installed correctly.

In summary, replacing a rear main seal can be challenging but necessary for maintaining your vehicle’s performance. It is essential to pay attention to any symptoms indicating wear on this component so that you can address them promptly. By following proper procedures and using specialized tools when needed, you can successfully replace your car’s worn-out rear main seal without causing further damage or issues down the road.

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