Might be time to fix 5-speed leaks

[Stainless]

Hi all,

Long time owner here. The only maintenance I've had to do for my 5-speed manual up to this point is replace the gear oil, slave, and master cylinders. The clutch line was already a SS braided line, thanks to the PO. While under the car recently, as I prepare to replace the original accumulator, I noticed the 5-speed is looking really crusty, meaning there have been unaddressed leaks occurring for a long time.

IMG_20200907_174643.jpgIMG_20200907_174650.jpgIMG_20200907_174659.jpg

I am mentally preparing to drop the tranny and address this long-neglected piece of equipment. I'd like to address all possible issues while I have it out, including anything that should be done internally. I'm confident that the rear main seal is contributing to some of the crustiness, as well as the seals for the output shafts. I'm looking to do it all, but not sure of all the issues or maintenance items I should address while I'm in there.

For context, the transmission performs very well. It shifts a little rough from 1st to 2nd when cold, but if weren't for the visible leaks, I would have no other reason to do this. The clutch is likely original. The car has around 53k miles.

What all should I plan on addressing?

[Mark D]

Looks like your transmission is doing an excellent job of incrementally disbursing rust preventative solution to your engine crossmember

Mine was doing the same when I first bought the car and the first thing I was told to check was the breather/vent on top of the transmission. It is known to get plugged and cause positive pressure to build inside the trans case when operating. After cleaning out the plugged vent the amount of gear oil leaking seemed to decrease, and after giving the transmission a good degreasing I was able to diagnose the leak as coming from one of the output shaft seals.

Before committing to pulling the entire trans out you may want to start with checking the vent and cleaning everything off really well to help pinpoint the leak.

If you end up pulling the trans it would make sense to replace the clutch while you're in there if it hasn't been done before. Same goes with the usual stuff you'd replace with the clutch like the throw out bearing, and possibly the shift fork/shift fork boot if they are deteriorated. With the trans pulled it may also be worthwhile to replace the 2nd gear selector shaft roll pin with a reinforced pin since they like to shear off and leave the trans with a spongy feeling downshift from 3rd to 2nd.

There is also a large nut on the end of the transmission for 5th gear that has been known to back itself off slowly and machine itself a hole through the end of the cover. Might be worth checking that as well and adding some red loctite.

[David T]

Unless you have other issues with the transmission, I would not pull it to fix some minor leaks. Get some Gunk and wash it. Even after you pull it and "fix" the leaks, you may still have some leakage.

[Josh]

Im no expert but it looks like you need new axle flange seals and a rear main seal for the engine. Both are common failure seals.
David, If you call this a minor leak I am scared to see what a major one is.

You do not need to disassemble the transmission to get to these seals but if you are taking it apart, It is common to replace all the internal roll pins and check over the bearings syncros. If you are planning for more power install a input shaft coupler. Inspect the 5th gear retaining nuts and re-install with red lock tite and stake the nut. Put the box back together with all new seals. This would also be a perfect time to replace the clutch, pressure plate, throw-out bearing, slave cylinder, and resurface the flywheel.

[FABombjoy]

rear main seal for the engine. Both are common failure seals.

It's worth cleaning the flame trap & ensuring PCV isn't blocked before figuring on replacement of the rear main seal.

Rear main seems like the first place excess crankcase pressure is noticed. For some reason the dipstick holds CC pressure better.

Years ago my trans looked a lot like the above, including the rear main leak. After new lip seals, flange repair, and improved PCV, all is dry!

[powerline84]

I had the same results as Luke. After converting to efi and modifying the pcv system and actually adding a pcv valve my leaks went down. I was pretty surprised.

[82DMC12]

It's worth cleaning the flame trap & ensuring PCV isn't blocked before figuring on replacement of the rear main seal.

Rear main seems like the first place excess crankcase pressure is noticed. For some reason the dipstick holds CC pressure better.

Years ago my trans looked a lot like the above, including the rear main leak. After new lip seals, flange repair, and improved PCV, all is dry!

Sorry to resurrect but what do you mean by the "flame trap" and the PCV? I know what a PCV valve is but didn't think our cars had anything like that. Does it have something to do with the hose that that connects the oil filler cap to the CSV? Or the hose that connects the black air filter cover to the oil filler cap?

[FABombjoy]

Sorry to resurrect but what do you mean by the "flame trap" and the PCV? I know what a PCV valve is but didn't think our cars had anything like that. Does it have something to do with the hose that that connects the oil filler cap to the CSV? Or the hose that connects the black air filter cover to the oil filler cap?

The oil cap contains a stainless or brass metal matrix. It's not on the maintenance schedule but should probably be cleaned at each oil change. It's really an air-oil separator that's not particularly effective, and even worse once it builds up junk. Volvo calls it the "flame trap" so backfires don't enter the crankcase.

Not my pic but a great example of what these can look like under the worst of circumstances
oil_separator_yuck.jpg

DeLorean PCV is a fixed orifice type system rather than PCV valve. A small orifice in the cold start tube provides best PCV at or near idle and light engine loads, and the big rubber hose to the airbox during medium & high load. The big tube is sometimes called the "fresh air inlet" but I'm skeptical that you can have anything resembling air move in to the crankcase with vacuum on the opposite side of the cap. You'll notice that your air filters get oily just above the plastic tube internal to the filter box.
Breather Tube.jpg

Fixed orifice types are K-jet compatible as they are a consistent "leak" downstream of the meter plate and the CO adjustment can be made around them. A traditional PCV valve would be preferred but K-jet can't compensate for the variable flow rate of a valve. Carburetors and EFI installations can.

[82DMC12]

The oil cap contains a stainless or brass metal matrix. It's not on the maintenance schedule but should probably be cleaned at each oil change. It's really an air-oil separator that's not particularly effective, and even worse once it builds up junk. Volvo calls it the "flame trap" so backfires don't enter the crankcase.

Not my pic but a great example of what these can look like under the worst of circumstances
oil_separator_yuck.jpg

DeLorean PCV is a fixed orifice type system rather than PCV valve. A small orifice in the cold start tube provides best PCV at or near idle and light engine loads, and the big rubber hose to the airbox during medium & high load. The big tube is sometimes called the "fresh air inlet" but I'm skeptical that you can have anything resembling air move in to the crankcase with vacuum on the opposite side of the cap. You'll notice that your air filters get oily just above the plastic tube internal to the filter box.
Breather Tube.jpg

Fixed orifice types are K-jet compatible as they are a consistent "leak" downstream of the meter plate and the CO adjustment can be made around them. A traditional PCV valve would be preferred but K-jet can't compensate for the variable flow rate of a valve. Carburetors and EFI installations can.

Interesting and thanks for the education! I assume the metal mesh could be cleaned with mineral spirits and the fixed orifice cleared out with some compressed air. I'll have to take a look at these (as well as the breather hole on my manual trans).

[Azar]

Hello, I am new to this please accept my ignorance. I have a similar picture and leaks as the thread starter. The Gearbox is dismantled and we are planning to change all the seals but also the front and back cover gaskets.
I was trying to find more information on the PCV bit couldn't. I presume it is Pressure Control Valve? Can someone pint me at the article which explains it exactly or probably point at the pats schematic so I can check it? The engine is disassembled, too. Thank you!

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