how to replace a rear main seal without removing the transmission

Bad. A rear main seal leak can cause some big problems in your vehicle. To make things worse, replacing a rear main seal can be one of the most expensive jobs you can do on your car next to replacing the head gaskets or rebuilding your transmission. But what makes a rear main seal leak so bad? In this article, we'll answer that question and help you identify whether or not you've got a rear main seal leak in your vehicle.

What makes a rear main seal leak so bad?

The leak location
The type of seal
The speed of the leak

Leak location

The biggest contributor to the cost of replacing a rear main seal is the location of the seal and therefore the location of the leak. The rear main seal in your vehicle is at the back of the engine and seals the crankshaft as it exits the engine. Your vehicle's flywheel or flexplate is then bolted onto the crankshaft flange sandwiching your rear main seal between your engine and transmission. To replace the seal, either the engine or transmission will have to be removed. Once one of those is removed the oil pan also has to come out so it gets to be an expensive job.

The type of seal

Some seals and gasket in your engine never cause large leaks because of the design or because they don't seal a pressurized portion of the engine. The rear main seal is subject to both high oil pressure since it is right by the rear main bearing as well as the spinning crankshaft which is constantly wearing on the inside of the seal. No matter how often you change your oil, eventually the spinning metal crankshaft will wear down the seal enough to cause a leak.

The speed of the leak

The possibility of a very fast leak is the biggest factor that makes it so dangerous to drive with a rear main seal leak. As we just mentioned, your rear main seal is in a place that gets a lot of oil thrown at it and has the added wear of the crankshaft spinning inside of it. If the seal tears or cracks at all your crankshaft rotation can cause the seal to get torn up very quickly causing a very fast leak. A fast leak can lower your engine oil level to dangerous levels very quickly and dangerously low oil levels can lead to permanent engine damage. For more information on why rear main seal leaks are bad, Join Clark in our garage for a quick explanation!

How Do I Know I Have a Rear Main Seal Leak?

Now that you know how serious a rear main seal leak can be, it's important to be able to spot one. If you've got a rear main seal leak you will have oil dripping off either your engine oil pan or the front of your transmission called the bell housing. The problem is other leaks can cause oil to drip from this location as well. For example, a leaking oil pan gasket or even a leaking valve cover gasket can drip down your engine and cause oil drips in this location. The only way to be sure you've got a rear main seal leak is to clean your engine thoroughly, then run your engine and check for the drip that looks like it's coming out of your transmission bell housing. If your transmission has an inspection plate you can also open that up and check for engine oil on the back of your flywheel or flexplate.

If you've discovered a rear main seal leak in your vehicle, seal the leak today before it's too late. Head to your local auto parts stores and pick up BlueDevil Rear Main Sealer . Simply add BlueDevil Rear Main Sealer to your vehicle's engine oil and your rear main seal leak will be stopped as your drive your vehicle.

BlueDevil Rear Main Sealer