Latest leaky transmission thread
09-22-2014, 03:37 PM
#1
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Latest leaky transmission thread
I think my first rennlist post was about a leaking transmission on my 1987 S4 automatic and not my latest one is too. 
This time is a bit different though. Typically my 928 can leak a little transmission fluid from the rear when it hasn't been used for quite a while during the winter and we have a really, really cold snap. no idea why, just does. And it isn't too much.
But about 10 days ago I noticed it was leaking again. Slow, not a lot. Also strange since I had just driven it about 2 weeks earlier. That's a while, but not too bad. I figured the seals might be drying or whatever. So I took it out yesterday but still a very slow leak. The strange thing is that it doesn't appear to just be leaking from the ATF reservoir. There were actually 4 spots on the drip pan showing a leak sort of spread out under the transmission.
Since this was a bit unusual, does anyone have any better ideas. I'll probably take it later to somewhere that has a lift so I can get a better look at it. But since I tend to worry about stuff like this, I thought I'd post first in case someone can give me a clue on what to look for.
Thanks in advance for any help.
-Bill
This time is a bit different though. Typically my 928 can leak a little transmission fluid from the rear when it hasn't been used for quite a while during the winter and we have a really, really cold snap. no idea why, just does. And it isn't too much.But about 10 days ago I noticed it was leaking again. Slow, not a lot. Also strange since I had just driven it about 2 weeks earlier. That's a while, but not too bad. I figured the seals might be drying or whatever. So I took it out yesterday but still a very slow leak. The strange thing is that it doesn't appear to just be leaking from the ATF reservoir. There were actually 4 spots on the drip pan showing a leak sort of spread out under the transmission.
Since this was a bit unusual, does anyone have any better ideas. I'll probably take it later to somewhere that has a lift so I can get a better look at it. But since I tend to worry about stuff like this, I thought I'd post first in case someone can give me a clue on what to look for.
Thanks in advance for any help.
-Bill
09-22-2014, 04:46 PM
#2
Nordschleife Master
Could be from the ATF lines' banjo bolt ring seals - these properly torqued ?
O-ring from the 'bowden cable' housing is another common site.
There are 3 hex head bolts which close off the testing ports for the operating pressure (R side), governor pressure (R side), and modulator pressure (L side) - these are other potential leak sites.
O-ring from the 'bowden cable' housing is another common site.
There are 3 hex head bolts which close off the testing ports for the operating pressure (R side), governor pressure (R side), and modulator pressure (L side) - these are other potential leak sites.
09-22-2014, 05:30 PM
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MainePorsche hit all the easy ones. The tough one is the front main seal which can deteriorate over time no matter how well you take care of it. Best way to know is to look for drips of trans fluid coming off the inspection grate for the torque converter housing. Fluid can drip out of here and cover the pan as it's upstream. I have a few threads on my past transmission R and R's and there are many others here as well - lot's of good info, search is your friend. And - I hope it's NOT the front main seal! Good luck!
09-22-2014, 05:53 PM
#4
Rennlist Member
There is a large o-ring that seems to always go bad on the transmission oil pump. It will leak fluid out from the TC grate. I have my transmission out for other work and am replacing this seal.