How To: Mustang Rear Main Seal Replacement (1982-2004 3.8L, 5.0L)

The rear main seal is located at the back of the engine block and has a very important job of keeping oil inside of the engine while the crankshaft rotates. Since the crankshaft protrudes from the back of the engine block, a seal is required to keep the oil inside of the engine where it belongs.

Most Mustang rear main seals feature a silicone, rubber or Teflon construction which wears out from age and the rotational forces from the crankshaft. Common signs of a failing rear main seal, is oil seepage around the bottom of the transmission, the bellhousing, or the spacer plate.

Replace the worn or damaged rear main seal in your 1982-2004 3.8L or 5.0L Mustang with this high quality rear main seal from Ford Performance!

Mustang Fitment: 1982-2004 w/ 3.8L or 5.0L

Item # LRS-6701A
MPN # M-6701-B302

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Late Model Restoration LMR SVE 5.0Resto ______________________________________________________

[SergeantExtreme]

On the other hand, rear main seal leak is the best undercarriage rust preventative you could ever hope for.

[toxictrack]

Them: "Grab a friend or two"
me: in the dirt on rhino ramps on my 15 monster, "I am a friend or two"

[SPURTIS]

That is gravy! It's about the easiest rear main seal replacement ever! Check out what it takes to do the same job on an older engine.

[joetcacciola]

My old seal disintegrated. I've spent two days pealing bits of silicone out of the groove. Getting to it was the easy part.

[scottmartin]

Just brought our 04 mustang to the shop today because I noticed the rear main possibly starting to leak. The mechanics said it's only "sweating" and as a friend he said he wouldn't put that kind of money into the car right now- it's 22 hours of labor, so in the end it's like 3 grand 😆 so I'm just gonna be monitoring oil levels, but at least it's not bad yet, sucks how much it costs.
Getting a subaru head gasket done, is about the same price.

[Scrapla]

Imagine reinstalling everything then finding out it leaks...

[Churchill]

While you're in there it wouldn't hurt to seal up the oil galley plugs back there. Mine were seeping.

[aaronmoomaw]

Ok so I have actually removed the transmission from the 02 mustang and it really isn’t that hard. It’s not he first thing I have ever done to a car besides oil changes and replacing a bumper and it just taking off bolts ( I removed the transmission to replace the clutch and I saw the oil leak so I am doing the rear seal as well now

[sarahdell]

Is this okay to use for something with higher miles? I have a 95 cobra that has near 100k. The seal doesn't leak but the trans is coming out.

[eldesgraciado]

Any transmission shop can do this for a fairly decent price. It's very easy to them.

[Dannymclovin]

Add a thin film of oil to just the outside of the seal or also the inside aswell?

[CreateYourWorth]

i need to replace mine, but waiting till I have to remove the transmission

[NathanielRatthamone]

My 3-ton jack n 4 stands are my buddies

[YoungMantv]

lol all the work dropping the transmission to replace the throwout bearing, clutch fork, pressure plate, clutch, fly wheel, AND the gasket ;)

[ChromeArty]

A little RTV were the clam shells meet and perhaps some blue locktite if them holes arent blind.

I gotta do this this to an ol ferd truck... might just let it leak, never done a tranny before (vehicle or otherwise)

[ChefBojack]

Mine is literally half disintegrated and caked in oil so it hard to get out

[edsel]

Is this the same exact way to perform this replacment seal on an 1982 Mercury Grand Marquis that has the V-8 302 engine?

[heathfiedler]

Just wondering if you can use Rtv pn a seal like this for extra sealing. I know it can be used on gaskets like the oil pan or others but figured I'd ask first

[gunners]

Do you need to drain the oil?

I'd imagine it doesnt sit that high in the oil pan, end up with a pretty foamy mess from the crank if it did right?

[JoseMedina-hsst]

Mine's just went out on my V6 2002. Mustang😢😢😢