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DIY Guide: How to Replace a Rear Main Seal Without Removing the Transmission

DIY Guide: How to Replace a Rear Main Seal Without Removing the Transmission

Hidden beneath the engine component of the vehicle is the rear main seal. The main responsibility of the rear main seal in your vehicle is to prevent oil from leaking between the block and the crankshaft. Many car owners associate oil leaks to trouble inside the car and it is fair to think that way. The rear main seal is designed to last for a long time, mostly, it lives through the life of the car itself. It is made to endure without having to be repaired and not be bothersome to the car owner. Understandably, the rear main seal also has its flaws. Usually because of its location and placement at the back of the engine, oil leaks are natural phenomena. The process in repairing the rear main seal most frequently requires the transmission to be removed but there are also ways car owners can undertake if removing the transmission is so much of a hassle. Read on to find out how to replace a rear main seal without removing the transmission.

Auto Repairs Are EXPENSIVE


Before diving into the repair of your real seal, you must first grasp some more understanding about it in order to know how to fix it. Repairing the rear seal for most people, even mechanics, is pretty daunting since you have to be familiar with the rear seal before you get into the fixing. What adds more to the challenge of handling this part is that it has different models. And differing models means differing processes in the repair. First off, why is removing the transmission the frequent resort to repairing the rear main seal? In answer to this question, one must have enough knowledge about the vehicles. Mechanics usually do this first step because the rear main seal is closely connected to the vehicle’s transmission components. The rear seal is difficult to reach so removing the transmission may be very convenient. It is located deep under the protective covers, wires and such. It is as if it is at the heart of your engine at the rear. So you would not have much luck if you intend to look for it without having to go through the other protective housing of your engine.


Primary to the repair of any car part is determining its location in the vehicle. Where can it be found? As indicated in its name, the rear main seal is located at the rear of your vehicle’s engine. The mind boggling thing is that most vehicles nowadays do not house the engine’s rear at the rear of your engine bay. Confusing ain’t it? But if you know your vehicle well, you will have done quarter to half of the repair job. Still, this information varies from vehicle to vehicle. In the case of a four wheeled car, the engine is elevated with its front towards the front of the car. In other all-wheel drives the engine can be mounted in a crosswise direction in the car.


Speaking of the seal, it would not be complete or even relevant if it is not used to fasten or secure something. The rear main seal functions to aid the crankshaft. What does the crankshaft do? The crankshaft and the engine’s piston are attached to each other, connecting them to the engine’s transmission as well. The piston is related to the starting process of the vehicle which means that the power of the engine is depending on it. SInce this is the case, the crankshaft carries a lot of the burden with the process in order for your engine to be able to move. The crankshaft has one of the toughest jobs in the engine because it is exposed to all the forces and power originating from the engine. The rear seal enters into the scene as it is the one responsible to hold out the oil from leaking into the crankshaft. As the crankshaft fulfills its responsibilities for the engine, it is inevitable for it to wear down the rear main seal if there is an oil issue with the engine or if the vehicle is not used for long intervals.


There are also other factors why most people choose to take the matter to the mechanics but mostly it is because changing the rear seal is a bit complex and time consuming. It also requires familiarity and level of knowledge of the construction of the engine in order to perform the task at an optimum level. Another thing is that the job requires special tools that most car owners cannot find in their normal toolboxes. Also, in the process of repairing the rear main seal, the vehicle may incur more need for repairs in regards to the small mechanical parts. This is the case with removing the transmission before getting into the main problem which is the rear seal. But, there is another way. Though it is not said to be easier but it is also manageable. You must follow certain procedures in order to have a do-it-yourself process with your car on the fly. So let’s get into replacing that rear main seal.


Friendly Reminder: Before you get your hands dirty with the work, prepare the tools you will be needing, keep the toolbox within reach. 


Step #1 Disengage the Battery from the Engine


Why is this step necessary when you will not even have to take out the transmission? Though you will not remove the transmission for this process, for safety purposes, you have to disconnect the battery. Carefully disconnect any negative and positive terminals connecting to any short circuit. You also have to take off the exhaust. This next step will help you have enough space to operate through the rear main seal.


Step #2  Take off the Driveshaft and the Flexplate


The driveshaft, also called the propeller shaft or the prop shaft, plays a part in the drivetrain of the vehicle. It delivers torque or power to different parts of the vehicle into the wheels in order for the vehicle to move. Driveshafts are used differently for different kinds of vehicles. But in order to replace the rear main seal, you have to remove the driveshaft. You will then get into the flexplate which is the last layer between you and the rear seal. The flexplate looks like a circular metal disc with holes into it. You have to remove this flexplate to enable you better access to the rear main seal. You can take off the flexplate with the aid of a wrench and a screwdriver.


Step #3 Take off Rear Seal Hood Remove the Rear Main Seal Hood


You are almost done. You arrived at the heart of your engine. Well, this is what you signed up for. You have to remove the rear main seal. Carefully take it off and install the new one. 


How does it cost to replace a rear main seal?


Most car owners choose to do the repair themselves because having the rear main seal replaced by the professionals honestly cost a lot. On average, the repair can cost up to $700-$850. The cost of the parts typically range from $35-$50 which. In reality, what makes the repair costly is the man power which will cost car owners from $600-$800 on average. Why is this the case? As has been mentioned above, replacing the rear main seal is a very time-consuming job. Especially if you bring it to the garage, the mechanics will have to remove the transmission and other parts of the vehicle’s housing in order to get to the rear seal and fix the problem. But, it is also wise to take into consideration that the cost of repair can also vary depending on the model of the car, add up to that the taxes and fees that may apply in different locations. No wonder many car owners choose to do the repairing and replacing with their own hands. So before you get down on the decision to have the rear main seal replaced, make sure that your diagnosis is correct, that there is really a problem that needs fixing. This will also ensure that you do not spend on something you do not even need. 


Is a rear main seal leak serious?


You may be thinking what the worst thing can happen if the rear main seal is damaged. Not only is the rear main seal responsible for the oil not leaking into the crankshaft, but it is responsible for the well-being of the car’s engine and the driver’s well-being. In short it is for your safety. So to answer the question, rear main seal leaks should be taken seriously. Apart from leaks being annoying and bothersome, it is also a sign of problems going on inside your vehicle. When the rear main seal is damaged, the oil leaks occur fast. Because the rear seal is connected to the engine, it would affect this part of your car greatly as oil starts to dry up and accumulate in that area, destroying the engine which may mean that the car will most likely have to go to the junkyard. Now no one would want that! So if you are having suspicions on your car, make sure to tackle the issue right away. If you want to know more about the causes of rear main seal problems or their symptoms, read on!

How many hours does it take to replace a rear main seal?


Replacing the rear main seal takes a lot of time and effort. As primarily discussed in this article, the usual first step in replacing the rear main seal is the removal of the transmission. And not only the transmission, the mechanic usually removes the whole engine first. You could just imagine how much time and effort that would take just to replace one thing. Not to mention, they also have to do the troubleshooting of the vehicle in order for them to diagnose the matter correctly. The seal is not the one that cost a lot but the process of removing it. That is why having professionals replace it for you is very pricey. Most repair garages will have you pay for the 3-6 hours of work. This is in the case that you will take the vehicle to the professionals. But doing the replacing and repairing on your own is a different matter. If you have the proper skills and knowledge, this may also save you time especially if you will not be removing the transmission anymore.


What causes a rear main seal to go out?


As for the ones causing the rear main seal to go out, it might not necessarily be the rear main seal itself but the other parts surrounding it. This includes the crankshaft. Though the crankshaft is designed to be durable and endure the stresses happening in the engine with the continuous torque the crankshaft has to supply, breakage can also happen in the crankshaft. This will in turn affect the rear main seal. Low quality installation work may also be one to blame for the rear seal going out. The atmospheric elements in different weather conditions such as dust and debris, also affect the vehicle’s parts.


As we all know, prevention is better than cure. And in order to protect yourself from further damage of your car’s engine and costly repair, you must watch out for the symptoms of a defective rear main seal. One of the most common symptoms associated with a damaged rear seal is the oil stains that are evident under the vehicle. Also, when the rear main seal is damaged, your engine is in danger of running on greater amounts of oil than it normally does. So if your car is demanding a lot of fuel lately than it does before, then you may consider having the rear seal to be replaced. 




At a last glimpse, replacing the rear main seal on your own may be a daunting task especially if you are one who is lacking the skills and knowledge of the system working in your vehicle. But the process being difficult does not really equate to it being impossible. Of course you can do it on your own. Though there are special tools that the experienced mechanic would use that you may not be able to find on your own toolbox, you can trust your wrench and other basic tools you have to be able to resolve your rear main seal problem. More than saving money, remember, safety should always come first.