How To Replace A Rear Main Seal Without Removing The Transmission

A rear main seal is an important part of the engine system. Its main function in your car is to prevent the oil from leaking between the block and the crankshaft. The rear main seal can last for a long time, maybe for the rest of your car’s lifespan. But everything has its down sides. When it comes to rear main seal replacement, it takes a lot of time. Usually, you will need to remove the transmission to do this process. But you may ask how to replace a rear main seal without removing the transmission? In this post we will show you how to replace rear main seal without removing engine.

What Is A Rear Main Seal?

If you want to know how to replace rear main seal, you will need to know what it actually is. Just like its name, the rear main seal is installed at the rear of your car’s engine. Its main job is to help the crankshaft. It prevents the oil from leaking into the crankshaft. Therefore, the crankshaft can finish its work and let the engine coordinate well. If the rear main seal is malfunctioned, the oil will leak fast. Then the oil will dry up and stay there will stains, destroy the system.

how to replace a rear main seal without removing the transmission
How to replace a rear main seal without removing the transmission (Source: Chevy HHR Network)

What Makes a Rear Main Seal to Be Ruined?

Besides the rear main seal lifespan itself, there are some other factors that cause the rear main seal to go out. First, it could be the malfunction of the crankshaft. When it leads to breakage of the crankshaft, the rear main seal will be affected. Second, the rear main seal can get into trouble because of bad installation from the producer or the mechanic. Also, the weather conditions and the temperature condition inside the car can affect the seal. Because of dust and debris, plus the hot or cold weather, the rear main seal may face with the threat of shortening its lifespan.

How to Replace a Rear Main Seal without Removing The Transmission

Changing the rear mail seal requires you to work hard for a long time. You will also need some special tools to execute this. Yes, you can ask a mechanic to fix it for you, but you will be surprise to know the rear main seal replacement cost. It will sweep your bank account like a broom. Usually, we will need to remove the transmission before reaching to the rear main seal. But you can do this rear main seal replace without removing the transmission. It is not less difficult than the other way, however, you can do it on your own.

Here are the steps of how to replace a rear main seal without removing the transmission

Step 1: Detach the Battery

The first step of how to replace a rear main seal without removing the transmission is to remove the battery from the engine. Although it is not involved in removing the transmission but safety first! You need to take the battery out. Disconnect both negative and positive terminals that are connected to the circuit. For generating more working space, you can also disengage the exhaust. Therefore, you will feel more comfortable later.

rear main seal replacement
The first step of how to replace a rear main seal without removing the transmission is to remove the battery from the engine (Source: Vestis Pluma)

Step 2: Remove Driveshaft And Flexplate

A drive shaft, also called a propeller shaft, is long rod that is designed to transmit torque from the output shaft of the transmission to the rear differential in a rear wheel drive, four wheel drive, or all wheel drive vehicle. Before replacing the rear main seal, you will need to take the driveshaft off. After that, you will need to find the flexplate. It is a round metal disc with many holes on it. Use a wrench and a screwdriver to help you with removing the flexplate. By doing this, you are able to reach the rear main seal easily.

replace rear main seal without removing engine
Before replacing the rear main seal, you will need to take the driveshaft off (Source: www.prestizwal.pl)

Step 3: Remove the Rear Main Seal Hood

By removing all the additional parts, you are almost done with the process of how to replace a rear main seal without removing the transmission. Generally, the rear main seal is pressed into the hood through bolts into the engine block. Here in the middle, you can see the crankshaft that comes into action when the engine is running. At the center of the crankshaft, there is a tiny piece, which is a pilot bearer. The seal hood normally has six to ten mm bolts that you must take off. After removing the entire set of bolts, remove the hood of the seal. Be careful while removing the housing of the seal as it is made with fragile material of aluminum that is prone to cracks and dents.

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Step 4: Remove The Crankshaft Seal

Normally the seal comes out with the hood but if it does not, you have to do it by yourself. Sometimes the seal is stuck into the crankshaft. Cautiously, poke the crankshaft to remove the seal. This seal is the rear main seal that you need to take off. Remove it and install the new one. This is how to replace rear main seal without removing engine easily in no time.

Why Having Rear Main Seal Replaced Is So Costly?

The steps on how to change rear seal on transmission seem to be complicated, why won’t we just bring the car to the garage? Well, some will be afraid of the sheer replacement charge. Read more for more reasons below

The Job Complexity

Rear main seal replacement requires a certain knowledge of engine construction as well as how it is attached to the transmission. There are different ways of installing the rear main seal as well as the transmission, so car shops have to charge a little more as each rear main seal will be a little different. Also, since so much of the vehicle has to be taken apart for the job, the mechanic need to know the transmission  and engine well enough to make sure all the other details don’t get overlooked and all the sensors get reconnected.

how to replace rear main seal
Rear main seal replacement requires a certain knowledge of engine construction as well as how it is attached to the transmission (Source: B & JJ Auto Repair)

Special Tools Requirement

The job will could require an engine hoist, at least and require a transmission jack, a wide range of torque wrenches, engine support bar, and possibly a bunch of other specialty tools to complete the job correctly. Repair fees for rear main seal replacement need to be high enough for the car shop to afford to purchase and maintain that much equipment.

Other Entailing Services

It can make sense to encounter other maintenance while you are replacing the rear main seal. For example, whereas the vehicle has a standard transmission, it may be time to replace the clutch as well since the transmission will be removed. In the same way, in case your engine needs to remove the crankshaft, it may be time to rebuild part or all of the motor. Also, some additional costs can be unavoidable like replacing the oil pan gasket if the oil pan needs to be removed.

rear main seal replacement cost
It can make sense to encounter other maintenance while you are replacing the rear main seal (Source: Edmunds)

Mechanical Parts

Mechanical parts are the smallest cost of the job but can add up to your bill quickly. You may choose to change other seals or gaskets or do any sort of engine rebuild, and then the costs of the parts can easily be accumulated up to a few hundred dollars more, in your replacement bill.

Conclusion

After going through all of the process of how to replace a rear main seal without removing the transmission, this task may be discouraging for many people. But if you can trust your own ability and your tool box, it will save you a lot of money. Otherwise, getting a mechanic will be also a safe choice so as not to waste more money on further breakdown. As always, we recommend you a regular maintenance check for your vehicle. By this, you will diagnose the car’s problem sooner and easier to fix it.