So im 99% sure that I have a leak from my rear main seal. There is a drip coming right from where the transmission mates to the crankcase. How difficult of a job is this in my own garage? I have a really hard time getting past the idea of paying someone else $500 to replace a $25 part. I figure my options at this point are to try it myself, suck it up and pay someone to do it, or try the oil stop-leak and face the consequences of that later on, or have it not work, and be back to options 1 or 2. Thoughts?

 

It depends on the engine. Some engines have a 2-piece rear seal. You can pull the oil pan and pull the rear main cap and replace both halves. Other engines have a 1-piece rear seal. You have to pull the transmission and flywheel/torque plate to change it.

 

I just got off the phone with my local mechanic. He stated that the seal on the 302 is a 2-peice rope type, more in common with packing than a modern rubber seal. He also said that it would be done as you said, pulling the pan and cap. This however is in direct conflict with the shop manual which says to pull the transmission and remove it from the back.

 

I don't think that's correct information. I'm pretty sure it's a 1-piece.

 

It has been my experience in the ford 8's and 6's I have taken apart, that the rear PAN seal leaks oil long before the CRANK seal does. (in fact, I have pulled out qutie a few 200K mile+ crank seals on tear down that are dry. bu the rear of the pan was doused.

in either way, its WAY WAY easier to yank the tranny to replace the pan gasket/seal - getting the seal to seat in the groove is hard enuf when you CAN see it...

 

It depends on the year if the seal is one piece or not. I had a 86 block that had the one piece rear main seal.

That being said, I agree with the last poster. Just because you have a drip at the rear/tranny pan, does not mean you have a "rear main seal" leak. You could easily have a leak at the front of the engine, and it will blow back while driving and hit the lowest part you are looking at and drip off. A simple valve cover leak at the rear will sneak down the rear of the block and drip right at the rear of the engine. A rear intake manifold seal can leak there also making it "look" like a rear main seal.

 

Rear main seals usually drip oil from inside the bellhousing, whether auto or manual trans. All other leaks described above tend to drip from the front of the plate between engine and trans.
I'd be removing the access plate (auto trans) to see if there is evidence of oil inside the bellhousing, or loosening the lower 1/2 of the plate (manual trans) to look for the same.

 

As some of you are aware, I recently (well, about two years ago by now) rebuilt my 400.
While the block was at the shop, I cleaned up & painted all of the remaining parts (bell
housing & T-18 manual transmission in particular).

Everything has been put back together and all new fluids everywhere, making it
particularly easy to identify drips. Similar to the OP, I also have a drip from between the
transmission & bell housing but, because the fluids are new and there is no grease or dirt
anywhere, I can easily identify the fluid and its source.

In my case, the drip is 90W gear lube which can be coming only from the front seal of
the transmission.

Point being (and has already been stated), just because there is fluid dripping from that
area doesn't automatically prove anything. No matter how you go about it, replacing a
rear main seal is a lot of time & work so it'd be in your best interest to be dang sure it's
leaking before tearing it all apart.

If your underside is dirty, I'll suggest adding some dye that fluoresces under black light
(NAPA sells it, prolly other places, too) to your engine oil (assuming your drip is, in fact,
engine oil) to try and help identify from where it's originating.

BTW I agree with the guys above - a rear main seal will leak into the bell housing, and oil
pan gaskets are FAR more likely to be a problem.

 

i just did my rear main seal on an 86 302 because it was leaking and blowing oil out the tranny. If you have a standard your clutch will start to slip because the oil gets in there. I dropped the tranny replaced the rear main seal and clutch fly wheel etc but ended up having a hell of a time getting the heavy np435 back in. So i payed some family friends at a local shop to pop it back in there. If he is charging 500 labor an will be replacing the clutch and everything else that really isn't a bad deal.

Bottom line. If it is a one piece than and you are SURE it is the problem I would say have him do it for you unless you own a nice strong tranny jack or have access to a shop. In a shop it is a really easy job.

-Dimitri

 

I have a L6 with similar problem. Mine is a dripper because the cork gasket is 29+yrs old. Once I decide to get under the truck, my oil pan replacement gasket will not be cork! I've replace the valve cover and tappet cover gaskets with neoprene type gasket. A little more expensive, but they will last.

 

good luck with that. none of my parts dealers could get me one in.

ford sells cork w/neo ends.

there is a number for one, but the engine has been out of print for 14-15 years and no one is replacing them...

 

FelPro #1820...not neoprene, but rubber/fiber...about $20 for my 300cid-6

 

Don't know what KIND of rubber they're made of, but Fel Pro #OS34601R is for a 92 300-6. It fits perfect once you grind off the raised surfaces around the oil pan bolt holes. The raised surfaces serve to hold the old (crummy) cork gasket in place; the newer FI engines don't have them because the rubber gasket has spacers built in to it.
Use the rubber gasket, and you won't have an oilpan leak again.

 

For my '81 engine the gasket I intend to use is the FelPro 1820.

 

FRANK.....I intend to follow your advice and use the one you suggested. Thank you very much for your help, I appreciate it.

BTW: grind off raised surfaces at bolt holes...ok Use RTV on block and pan? I'm ancient working on the driveway in the Texas heat, and under the truck is tough on me so I want to do right the first time. Gotta take the Radiator off or no? thanks

Dave