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Ndawg12

Another thing to Check - Tranny Breathers

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Ndawg12

I have an ATF leak coming from my transmission again this year.  While researching I ran across an interesting post from @Bawshogg about how he questions the breathers on the vdrive and tranny because when you crack the fill/dipstick you hear a swoosh and a release of pressure.  I thought to myself, I know mine does this but always thought it was normal.  I took a look last night, the vdrive did not release pressure and the cap on the breather spins freely.  The tranny released a little pressure and I found the breather cap to be stuck and painted in place.  I took some pliers and was able to break it free.  I figure I'll let it go through a few temperature swings before I crack open the dipstick and check for a pressure release.  

So my question is: how plausible is it that my leak is due to the breather being stuck all these years and pressure constantly being applied to the gaskets/sealants that mate the sections of the tranny together?  

 

For your reference ZF45C

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robbennett

Hmmm you have given me something to look into. I always wondered why there was pressure in it but really haven't seen any leaks. 

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Chaabo

Same here, always wondered about that on my Response.

I have no oil leaks, but it's like opening a pressure cooker, when I check the oil level.

Where's that breather located on a DD, can someone point me in the right direction?

Edited by Chaabo

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minnmarker
3 hours ago, Ndawg12 said:

So my question is: how plausible is it that my leak is due to the breather being stuck all these years and pressure constantly being applied to the gaskets/sealants that mate the sections of the tranny together? 

@Engine Nut could probably tell us.  I've wondered the same.

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Woodski

@Ndawg12:  Going under the assumption the leak is coming from a location that should be sealed (gasket), most likely not due to a moderate amount of pressure internal to the trans.  If it were coming out a vent, yes, but a gasket or sealed joint should easily seal against a slight internal case pressure buildup.  ATF has excellent wicking properties, is also very light in viscosity so it will find the smallest of breaches to escape.  With the properties of ATF be extra diligent in determining the source of the leak, it can surprise you as to where it is coming from.

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Ndawg12
Just now, Woodski said:

@Ndawg12:  Going under the assumption the leak is coming from a location that should be sealed (gasket), most likely not due to a moderate amount of pressure internal to the trans.  If it were coming out a vent, yes, but a gasket or sealed joint should easily seal against a slight internal case pressure buildup.  ATF has excellent wicking properties, is also very light in viscosity so it will find the smallest of breaches to escape.  With the properties of ATF be extra diligent in determining the source of the leak, it can surprise you as to where it is coming from.

Agreed, it actually doesn't appear to be coming from the same location that I repaired last year.  I'll try to pinpoint the source later today and report what I find.  Anyone have decent pics of one of these units pulled out of a boat sitting on a bench or something?

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Ndawg12

Well the 2 bolts that I blindly pulled Thursday night happened to be a cover plate for the filter/screen of the transmission.  So Friday I cleaned up nearly 2 qts of atf from the bilge, sanded and prepped the matting surfaces on the tranny and plate, applied ATV sealant to the plate, and reinstalled everthing.  I'm really hoping that the leak was coming from 1 or both of the filter/screen cover plate.  I'll refill tomorrow...

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electricjohn

Was the screen clean?  IIRC, there is a rubber gasket associated with that cover?  No?   I'm guessing the breather you freed up is on top of the tranny?  good luck.

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Ndawg12
22 minutes ago, electricjohn said:

Was the screen clean?  IIRC, there is a rubber gasket associated with that cover?  No?   I'm guessing the breather you freed up is on top of the tranny?  good luck.

Yes I believe the screen was clean, until it dropped into the bilge.  You insert the screen, then the rubber oil plate, and then the cover plate.  I'm glad I added the RTV because the more I think about it I'm suspecting that rubber oil plate to be the culprit.  See page 18 on the link above.

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Nitrousbird

Hmmm...never noticed a breather on mine nor have I heard a woosh when opening either.  Now I'll have to take a dang look in the spring!

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tvano
On 2/24/2017 at 0:28 PM, Chaabo said:

Same here, always wondered about that on my Response.

I have no oil leaks, but it's like opening a pressure cooker, when I check the oil level.

Where's that breather located on a DD, can someone point me in the right direction?

i'm guessing that the breather is located next to the blue label and is kissing the coolant crossover hose.

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gorilla
1 hour ago, tvano said:

Yup, that's it. You could tear the cap off that and put a hose and PCV filter on it. That's what I did on my 4Runner to extend the rear axle breather up high, for deep water crossings. 

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Engine Nut
On Friday, February 24, 2017 at 11:32 AM, minnmarker said:

@Engine Nut could probably tell us.  I've wondered the same.


 

On Friday, February 24, 2017 at 11:32 AM, minnmarker said:

@Engine Nut could probably tell us.  I've wondered the same.

The whoosh you hear when removing the dipstick is air coming back into the transmission. As the transmission gets hot, the air in the transmission expands and exits via the breather which is a check valve that lets air escape but seals off and does not let air or water come back in ... so it draws a partial vacuum in the transmission. That is why it is important that the bilge doesn't have water in it particularly above the level of the output shaft because the partial vacuum in the transmission can actually suck water past the output shaft seal and into the transmission as things cool down.

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BlindSquirrel
On 2/26/2017 at 5:17 PM, gorilla said:

Yup, that's it. You could tear the cap off that and put a hose and PCV filter on it. That's what I did on my 4Runner to extend the rear axle breather up high, for deep water crossings. 

Me too! You must be a member on t4r.org

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gorilla
2 hours ago, BlindSquirrel said:

Me too! You must be a member on t4r.org

Hahaha, that modification has been all over the internet. I did it around circa 1999. But, never been a member on there. 

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