Thunderbird SC
Ford Rear Main Seal

Please read this before doing any work

Table Of Contents:

Section 1 - Introduction

Section 2 - Items Needed

Section 3 - Removal Of Tranny

Section 4 - Removing Old Seal

Section 5 - Installing New Seal

Section 6 - Reinstalling Tranny

Section 1 - Introduction Rear Main Seals are a problem with most vehicles. The seal is between the crank and the block and it is what keeps oil inside the engine and stuff out. Symptoms are rather easy to spot, there will be oil leaking from around the rear of the engine. It can be on either side of the separator plate, but is generally on the tranny side. Some minor leaking is not a major problem, but if it drips really badly then a new seal is in order.

The process of removing the seal and installing a new one is rather simple, but getting to the seal is the hard part.

Before you begin this work please know how to remove your tranny. There are two other walkthroughs on this website that discuss how to remove the AOD and 5-speed. (AOD to 5-speed swap and Aluminum Flywheel).

Some interesting information that was sent to me by a fellow thunderbird lover.

Given that the SC uses a one-piece rear main seal there is a product available that is a slip ring that can be fitted to the crank that will form a new sealing surface. One older cars the reason the seal often leaks is that a shallow groove is worn into the crank sealing surface which allows the leakage to begin in the first place. Just replacing the seal with a new one does not overcome this problem and it will begin to leak again shortly. The groove is caused by friction between the rear main seal and crank that over the years causes the wearing of this groove. The "Slip Ring" restores the sealing surface.

Section 2 - Items needed


  • 1 - New Rear Main Seal
  • TOOLS:

  • 1 - Sharp, Thin Knife
  • 1 - 90 tip, flathead screw driver
  • 1 - 3" diameter X 4" long piece of pipe
  • Section 3 - Removal Of Tranny Please read the AOD to 5-speed swap or Stock flywheel to Aluminum flywheel swap walk-throughs for this information.

    Section 4 - Removing Old Seal Other than the removal of the tranny, this is the hardest part. Be very careful not to knick, scratch, or otherwise damage the races in which the seal resides. Doing so will cause leaks that are not fixable without doing some grinding.

    First thing you want to do is to take your knife and cut the seal. You will be making a circular cut (around the inner parameter) that is inside the first lip on the seal. If you look at this picture you will be cutting along the inner part of the indented rectangles. This will give you a large enough gap between the crank and the remainder of the seal to get your 90 bent tip flathead screwdriver in. Once you have it in, you can pull outwards on the seal, working your way around. It's a slow, gentle process, but you will be able to pull the seal out.

    Section 5 - Installing New Seal Take the new seal out of the package and apply a small amount of clean oil to the inner and outer surfaces. Place the new seal around the crankshaft and push it gently into place. Now take a 3" pipe (I found that the thick-walled black works best) and gently tape the seal in evenly, making sure not to bind it up.

    This process will take a little while, but the end result is a new seal that is flush with the block. Don't hammer it in too far.

    Section 6 - Reinstalling Tranny Please read the AOD to 5-speed swap or Stock flywheel to Aluminum flywheel swap walk-throughs for this information.

    Use of this document and anything contained within these pages is at the users own risk. By using this information contained herein you shall not hold TBK, TBKHomeworld, or any of it's parties responsible for any damage to your car or injury or death to yourself or any persons, animals, planets, or objects. Please be careful when you perform this work. Follow all safety procedures listed here and everyday safety procedures. USE YOUR BRAIN! Please be kind to the environment and dispose of toxic chemicals and substances properly.