usmarinejohn

I'm seeing a drip from the housing below the transmission behind the engine. I believe that's probably the Rear Main Seal between the engine and transmission. Can anyone tell me which one I should remove in order to replace the seal?

I'd prefer not to pull the engine if I don't have to. I've heard that it's possible to remove the transmission, or to unbolt it and move it back enough to replace the seal?

Any help would be great, thanks!

Shark Racer

Assuming this is the original motor or original style (most likely), it's a 2-piece rear main seal and you have to drop the oil pan to get at it. Not *too* bad.

Believe some of the steering linkage has to be disconnected to finagle the pan out. Then you pull the rear main cap, bottom half of the seal comes out with that and you use a little plastic tool to poke the top half out.

Take a look in search, and there should be plenty of advice on the subject.

"rear main seal" is what you're interested in.

usmarinejohn

I did see some other posts that had similar info. That's good news, I was expecting to have to do alot more work than that. Good news is I already have a new Power steering arm to install, and an oil pan gasket so both of those are coming off anyway.

Yes, it's the original rear main seal so I'm sure it will be the two piece.

thegazman

If you look at "Vettetech's" web site there a detailed article with photos on replacing the rear two piece seal under misc.

SOMFormula

Some advice:

Drain the oil the night before pan removal!
Otherwise, oil will be dripping on you the entire time your working on it.

Use a soft metal punch to free up the upper portion of the RMS.

Permatex makes the anerobic sealant in a small tube for about $6 at Napa.

Set aside an entire day to do this. Not a difficult job, but I like to paint the pan while its off an spend some time cleaning under there.

The most difficult part of the job is getting the oil pan on and off. And that's not that hard! The rest is pretty simple.

Good luck!

brando1118

Hi usmarinejohn,
An oil leak from anywhere on the top rear of the motor could end up looking like a rms leak at the bottom of the bellhousing because that is where the oil will end up right before it drips on your garage floor. Might be worth a look at valve cover gaskets, intake gaskets, oil plugs at the rear of the block,etc..

Also it's not the age of the seal that dictates whether it's a two piece rms, it's the age of the block. If your motor is original and you have a C3 it's gonna have a two piece rms. If your motor is not original look at the casting numbers at the rear top of the motor. If the year of the block is 1985 or less, it's a two piece rms. 1986 and up *should* be a one piece rms. Check for oil leaks elsewhere so you don't make more work for yourself.
Good luck.

mlars

Last time I replaced a rear main seal that was a two piece, I had to do all of what has been said and loosen all the mains to relieve the pressure on the seal to get it out. Still doable just tourqued them back down per specs.

jackson

very good oil pan gasket for '80 C3 is a one piece silicone and it has new bolts AND the snapups that really help when doing this job with motor in car ... it's usually available local for about $25

fel-pro p/n OS34510T

scottyp99

OK, we may be putting the cart before the horse, here. I think the first thing he should do is determine whether the leak is engine oil or transmission fluid, and go from there.

The rear main seal is part of the engine, it's not "between" the engine and the transmission. The only thing that can leak from it is engine oil. (I suppose, in theory, something else could leak from it, but in that case, you have WAY bigger problems than replacing a seal!!) If it turns out to be tranny fluid, there is no need to replace rear main seal. If it is oil, it might not be from the rear main seal. I apologize if it sounds like I am talking to you like you are an idiot, it's just that it sounds like there might be some misunderstanding here. That being said, if there is something leaking from the area where the engine and tranny meet, it's a pretty good bet that it's the rear main seal. The old 2-piece rms is famous for it. Good luck!


Scott

usmarinejohn

Thanks for the post, I prefer to be talked to like an idiot, it makes things much easier!

Yes, it's engine oil, and no, I didn't know that the rear main seal was part of the engine, never had to replace one. Well, I take that back, I replaced the main seal on a 68 VW bug - as you can imagine that was alot different. I'd rather replace the old seal with something that I know won't leak, I'll look for the one piece. Thanks!

MotorHead

Some good advice above about making sure where the leak is. Probably a few thousand RMS's have been replaced and the leak is still there, I can't think of anything more aggravating...oh yeah I can

Do yourself a favor and get an Oil Detection Kit from Napa, you glasses and UV light an 2 vial of dye and you will know for sure where the oil is coming from. Most of the RMS leaks are leaks from the back of the intake and it travels down to where yours is dripping. It goes to the lowest point in that area.

The kit can be used over and over with new dye bottle that are cheap

scottyp99

The back of the engine is tough to get at, but what I like to do when trying to track down an oil leak, is clean the area thoroughly, and spray it with some aerosol foot powder. The leak shows up against the white powder amazingly well.


Scott

cv67

The "one piece" seal they are talking about is merely for the oil pan itself, the rear main seal is a little more wrench turning to get to.