That metal gasket eng/trans realy needed?

If you do not use the gasket and just use an anaerobic sealant, it may work for a while but I'd expect it to leak eventually. You are sealing aluminum to aluminum (front & back covers to trans) as well as cast iron to aluminum (block to trans). All those dissimilar metals with large sealing surfaces have different expansion rates and I doubt any sealent would last very long after it went through about 300 heat cycles under those conditons... When saab used the paper trans to engine gasket, it was a frequent point of leaks. When they switched to the metal gaskets, those problems went away.

If you want to risk it and just use a sealant, it might work fine. Use the metal gasket, and it WILL work fine.

I doubt that it would leak, because aluminum canot expand more than block because too many fasteners are used. I am building an engine now and I just want to go "green" on it, using all silicone exept for head gasket and valve cover gasket. So far I had great results with "ultra gray" silicone.

Delorean is correct. Learn from my mistakes. It doesn't take much movement to ruin that anaerobic gasket. I was low on cash and used ultra-black instead of the metal gasket. 10k miles later I have oil seepage. It's very minimal, but nonetheless I will need to replace it soon.

you can use "ultra gray" silicone on C-900's but I would highly recommend against it on T5 & T7 cars. Keep in mind, for the silicon to have any chance of working, you need very clean surfaces, preferably clean them with brake clean before application of the silicon. It also must go on very thin, do not "gob" it on. You can be a lot more sloppy with the lock-tight anaerobic sealant, as it dissolves in oil. The Silicon does not, and can plug critical oil passages if it gets in places it shouldn't.

Do you use silicone on the front and back of the metal gasket or all the way around ?
I have swapped my tranny before. But the first time it wasn't 100% sealed and this time it is even worse. I have a little oil puddle under my car every morning. I wonder what I am doing wrong. Seems to leak at the front of the engine on the exhaust side. Hard to tell if it comes from the tranny seal, the screws or where the turbo return line hits the engine.

Look in the Bentley manual, it shows where you need the sealant with the metal gasket. it is not all the way around, it is just around the front and rear cover areas, which allows for expansion.

I used anaerobic sealant last month. I was pretty sloppy with it, and it doesn't leak. 6k miles.

Crap. Seems like I have to pull the engine again

Raul said:

I doubt that it would leak, because aluminum canot expand more than block because too many fasteners are used.

Click to expand...

This is not true, it's the reason there are things like MLS head gaskets, so that the relative movement from thermal expansion is more uniform. Just because there are lots of fasteners doesn't mean the pieces are held together perfectly rigidly.

That being said, I know that there are cars we have serviced at the shop where they omitted the metal transmission gasket, and I do not believe any of them leaks (or at least leaks a LOT).

I used the metal gasket and Loctite 518 on my build 8 or whatever years ago with fresh tanked surfaces on the block and both covers, and it leaks.

Best,
Drew

Yup, I'm currently pulling my engine to redo this, AGAIN. I just finished the rebuild on my C900 and it leaks like a bitch on the rag. Don't cheap out man, I do the worst hack jobs of all time, I once had an oil feed line nothing but JB Welded into theoil filter housing; but you don't want to screw with this one. I put the gasket in, but I forgot the sealant. I've worked on alot of Saabs but this one blew my mind. Gasket AND sealant. Cars been registered for 2 weeks and I've only driven it once, I'm pissed off like you wouldn't believe. Do it right, its one of those things you go, "Aww shit, THAT things leaking? Ohhhhh f******* me"

Tom

Yea, I agree. F***. And I though I did it the more correct way...

It's so nice to have Raul back.

aireeca said:

It's so nice to have Raul back.

Click to expand...

Mods, please arrange Raul vs. VL cage match.

Ulta grey i wouldnt use,, it can clog the oil pickup pretty quickly anaerobic will never do that

the big reason is because this motor/trans was designed before good chemical sealants (late 70s???)

ive taken the motor out of the car for this exact reason, the other big thing that can cause these to leaks is a faulty check valve to the PCV system,,

boosted crankcases cause alot of leaks

If one is building a motor, why not just spend the extra $20-30 for the correct gasket? In the big scheme of things, such is really pennies. Why take the risk to save such a small amount?

aireeca said:

It's so nice to have Raul back.

Click to expand...

Indeed! The only reason I posted in this thread to begin with.

Never had to deal with this, but I believe SAAB put out a TSB saying, "just use 518."

Saab used to use paper gasket for timing chain cover and back engine cover, and paper would just loose it over time and leak. So Saab discontinued those gaskets and told to use silicone there. I used ultra gray silicone on those locations alone and after 10 years it does not leak. Black RTV is not good enough it is made for lower temperature parts will little stress. I think the reason why they don't want you to use silicone on the tranny to engine is the surface is large and non experienced mechanics would put too much and that silicone may go into oil pan plugging the oil pickup screen.
I installed pistons from T7 car on this old B202 block, it looks great.