318 rear main seal replacement

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If you look at the halo around the oil drip forming, it sort of looks red.

I think cleaning it up and placing a white paper towel underneath it on something dry, like a piece of cardboard and cranking it/ creating a leak would be the ideal way to check which kind of fluid you are dealing with, before tackling.

Also, just a quick/ dumb check, grab your socket and see how tight the pan bolts are. Sometimes they come loose and can be tightened up enough to eliminate a leak or at least slow it down to a point that it's negligible to deal with, at the moment.
 
The red is the degreaser I used, turns everything like that.
Gonna crawl under there right now and take a looksie, I'll report back later.
 
dumb check seems to have solved the issue, one bolt in the rear was loose enough I spun it with my fingers......so I tightened them all up. Cleaned the area and cranked it till the oil pressure came up and it's bone dry, nothing coming out.

I'm debating about pulling the engine/trans though since the trans is leaking and it'll just be easier to work on that way. Might just replace the rear seal anyways since the engine would be out and on a stand.
 
Good deal.

Maybe pull it if you want to start hotrodding. It depends on how much work you want to do. If it runs for now, if I were you, I'd leave it alone and enjoy it this season, before tearing it down. Where is the transmission leaking from? Contrary to oil leaks on the engine, transmission oil leaks are exceptionally easy to remedy from under the car.

If I were you, I'd enjoy it for a year/ nice weather season before pulling anything apart.
 
Yeah, where in Cali are you if you need I have an engine hoist you can borrow
if needed.
Luke
 
Those are both O rings. The speedo gear can be pulled and the ring replaced without anything else.

The transmission pan has to come down, kickdown and shifter arms off of the shaft and the valve body has to come down, to replace the shifter/ kickdown shaft O ring seal, but that's about a 1 hour job with a beer.

If you've never drained a 904/ 727, get ready. It's going to get all over the place. Just do yourself a favor ~ get a filter kit for the gasket (new filter isn't a bad idea to put in, anyway) and some new fluid, loosen all of the bolts about one full turn, wedge a flathead in the lowest corner (this is where a sloped driveway can actually help you) and twist the screwdriver so it slowly comes out. If you need more, loosen the two adjacent edges of the pan to that corner, before loosening the rest, a little at a time. Get a drain pan with a big catch area that will cover the entire pan area.

When you get the gasket out of the box, put it on something flat, put an old shirt over it and iron it. Then, after you scrape the trans and pan, tac the gasket in a few spots with some RTV and put it on the pan, then tie it up at the corners first with the bolts.

While you're down there and the fluid is out, go over to the passenger side and take the dipstick tube out and replace the O ring on that.

Then, the only old seal you'll have left is the tailshaft to output yoke seal, but if it's not leaking, leave it. If it ever needs replaced, just nose the car down the driveway and you won't have to drop the fluid to do that one.
 
I installed a shift kit a few months ago in it haha, then found that the seal is leaking, I think. Still have to pinpoint it but it shouldn't be that bad if I do. I put a drain plug in the back of the pan when I did it as well so that should help.
Just a bolt with a washer ontop to pull the new seal in or something like that should work for the one in the case.
The rear seal is leaking..again....so I have to replace that too haha.
Thanks for the help.
I'm located about 30 minutes out of San Francisco
 
While you have the valve body out,, there's also a small seal inside the piece that protrudes out the trans case,, it seals between the throttle pressure lever shaft and the outer piece.. It's often overlooked,, and you might as well change it too..

Same with the speedo gear,, along with the O-ring,, there a small seal that fits between the gear and the gear holder,, change it while its out..

I usually use a small slide hammer poked up thru the hole, with a nut and washer.. a bolt, and spacer would work..

I've also found it helpful to take the seal to a grinder, and put a small chamfer on the starting edge, and use a little sealer on it....

hope it helps..
 
sounds good, the main leak is coming from the speedo and then from somewhere up front ish, still need to pin point it but it's too late for that tonight
 
You can do the upper and lower with the motor in the car, heck I did the entire crank R&R in the car once! pull idler arm out and drop center link. drop pan, turn crank so the throws clear and then pull pan out front, it should clear pickup too. pull rear cap, use screw method or Lisle "sneaky pete" tool.
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pull old one out and pull new one in. You can also remove flex plate bolts and main caps and you can pull rear of crank down about 1/8 inch to help install new one or remove old one. It wont move much but maybe just enough. Stagger rubber seals so it doesnt match cap mating surface, this helps seal it, and use plenty of oil in the installation. run all bolts into pan first then tighten in a criss/cross pattern to about 10 ft lbs, just snug. Its not that hard, all upper bearings can be 'rolled' out with crank and a heavy paper clip formed into a T and put into the crank oil hole. Itll will catch on bearing and push out when you turn crank. #3 Thrust bearing may not be doable with crank in block this way.
 
pishta said:
Stagger rubber seals so it doesnt match cap mating surface, this helps seal it, and use plenty of oil in the installation. .
Click to expand...

You been working on too many chebbies, lol ..

mopar seal only goes in one way,, (the piece with the tabs, goes into the brg cap..)



and dropping the crank is unnecessary..

cheers
 
RE: trans leaks, the dipstick tube O ring is also a notorious leak source.
 
I hate trans leaks...did saetuns a while back and now it's a mess...gotta redo it.its driving him nuts....
 
Read through here and it sounds like you have gotten some solid advice. Speedo cable has 2 O rings..simple fix. Your initial pic is of the pan and not rear main seal. Further along Inertia posted a pick of the rear main seal that is rubber. With those tabs I an not sure how you would replace without motor out of car....you can's slide that sucker. I just installed those on my 318 build. I agree with DaveBonds...drive it, spring is coming and it you may be better off to wait until you plan to make some upgrades on drive train! Good luck!!
 
DaveBonds said:
The upper seal was rope on my '73. I replaced it with the rubber one. I can almost guarantee that yours is rope, too. They are no more difficult to replace than rubber, but having a rope upper and rubber lower might be tricky to seal. You could try RTV at that junction, but I don't know that the rope being saturated in oil will ever take the RTV completely. It might slow the leak down significantly, though.

Either way, just taking the rear main cap off won't do anything to get to the upper, because it's above the crank, in the block, itself, along with the rubber blocks that seal the main cap to the block and the lower, within the main cap.

The issue with the pan isn't what is under the pan, it's what is inside the pan, down below the bolt/ gasket line that will make your life hell, with the engine in place. You have to get the pan down far enough to clear the crank at the very front, but even if you rotate the crank so that the counterweight for the 1/2 piston journal is up and out of the way, you still have to move it around the pickup in the sump.

You shouldn't have to take the engine out, or the water pump/ timing cover if the rear main lower seal is what is leaking.

Do you know what your timing chain looks like, or how long ago it was changed?

The reason I ask is that if you've got the car apart down there and the car is out of commission, it would probably be a good idea to change the chain. A rear main seal leak is usually not the only part of the bottom end that needs maintenance, when it goes, unless it's a fluke.

I think it would be wise to do upper and lower seals, or just wait on it, save some cash and pull the engine to clean up and put new gaskets on everything, with a new chain, all at once.
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I've replaced a seal in a 318 without removing the crank more than once. You have to break the mains loose, but you don't have to completely remove them to do it.

Pull the rear main and oil pump, loosen the other main caps, and then take a small screwdriver and push the upper seal out from the block. It will come out.

When you go to put the new seal in, dip it in STP oil treatment, and work it in around the rear main journal until it seats, then put the rear main cap on, torque the main caps back down, and reassemble your oil pan.

Do not pull the engine if you don't have to, it's a big wast of effort and time.
 
Dartn440 said:
Read through here and it sounds like you have gotten some solid advice. Speedo cable has 2 O rings..simple fix. Your initial pic is of the pan and not rear main seal. Further along Inertia posted a pick of the rear main seal that is rubber. With those tabs I an not sure how you would replace without motor out of car....you can's slide that sucker. !
Click to expand...

DaveBonds said:
Either way, just taking the rear main cap off won't do anything to get to the upper, because it's above the crank, in the block, itself, along with the rubber blocks that seal the main cap to the block and the lower, within the main cap..
Click to expand...

inertia said:
mopar seal only goes in one way,, (the piece with the tabs, goes into the brg cap..)



and dropping the crank is unnecessary..

cheers
Click to expand...



As I mentioned earlier.. THE SEAL WITH THE TABS FITS IN THE CAP ! ! ... sheesh
 

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The only thing I mentioned was taking the rear main cap off doing nothing. You would have to loosen all of them, as stated. I still stand by the statement, in that just removing a rear main cap would do nothing.
 
Geez DaveBonds,, I don't know what to tell you,.. I had a great mentor, breaking flat rate with no come-backs was his deal,, we both held records of max flat rate a day at respective dealerships, everything he taught me was quick, efficient, and if there was a shortcut,, he knew it.. ( He participated in the Mopar(?) challenge wayy back))

He showed me how to take the rope and rubber seals out without loosening the maincaps, in MOST cases,, I won't say I never had to loosen the mains,, but my mentor said leave the "crush" on the brgs if you can.. So for 40 yrs, I've been doing regularly what you say can't be done.. lol

I think it comes to commitment,, you see, not knowing it can't be done,, I always approach the job knowing the seal WILL come out,, so it does,, if you keep approaching it,, "I gotta drop the mains,, undo the bellhousing, (that's a good one) whatever"".. then it's gonna go that way..

I seldom use a "pickle fork" for ball jts/tie-rods etc,, cuz He taught me that if you hit them just right, they'll pop on the 2nd or 3rd hit, with my 40 oz ballpeen of love.. commitment.. lol

That main cap I showed in the pic,, I just took it off of an engine I'm about to do,, After Brunch,, I'm gonna go down to my shop,, and because I'm committed,, "'Im gonna PUSH the other half of the seal out of the block,, with the mains still tight,, I'll show you the result..

So.. To anyone following this thread, and needs to do a rear seal,, try without undoing the mains first,, and do not loosen the trans,, I've never had to do that in any breed,, and I think I done most common older ones.. cheers

hope it helps.
 
I don't have time to go pop that seal as I have family over,, and I know it'll push out anyway,,

The factory service manual does not appear to have an "in Car" seal replacement,, but here's what my Chiltons Shop manual has to say,, supporting my claim you can get the rope and upper seal out with out lowering crank,, and while it suggests lowering the crank to "ease" seal installation ,, I maintain the lip of the seal is flexible enuff to work it in while rotating the crank (the crank will actually drag the seal into the groove), so you don't have to drop the crank,, and I have done so many, many times..

I'll supply pix of upper seal removal tommorrow,, when I won't get my butt chewed.. lol.. family day..
 

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I'm going to drive it for now, seeing as it's stopped leaking from tightening the bolts on the pan. Next time I'm pulling the engine hopefully it's to drop in a magnum and a518. Going to order the seals this week.
 
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