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Odd 727 tranny leak!
#293058
04/19/09 05:40 PM
04/19/09 05:40 PM
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Joined: Sep 2005
Posts: 1,202
California
polkat
OP
mopar addict
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OP
mopar addict
Joined: Sep 2005
Posts: 1,202
California
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Bought this '73 D-100 truck as a project last week. I was told that the tranny (727) had
a front seal leak, that it was fixed, and that it came back shortly afterwards. Okay says
I, some more fun work! Today I took a look for the first time. Now, thinking about the 727,
if the front seal were leaking, the only place it could come out is at the inspection cover
on the front of the bellhousing (which is integrated with the case).
But my inspection cover, and indeed the whole bottom of the bellhousing, is dry as a bone!!
The leak (only when it's running) is right over the crossover pipe for the exhaust, and
directly above it is the front of the tranny pan. And that area is wet! To me, this
is where it seems to be coming from as I watch it.
So my question is, does returning fluid flow over the inside of the front pan area
when the pump is running? The outside of the gasket looks pretty bad, so I'm hoping
all I have is a bad gasket and not a front seal leak.
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Re: Odd 727 tranny leak!
[Re: polkat]
#293059
04/19/09 06:03 PM
04/19/09 06:03 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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While you have the trans pan off, lay it on a flat surface and check the area around the front of the trans pan. My wifes car leaked at that exact same spot and the pan rail ( gasket surface ) was not flat in that area. A hammer and a fresh gasket fixed the problem. Also check the dip stick tube area ( right front of the case )for leaks. It's close by.
Fastest 300
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Re: Odd 727 tranny leak!
[Re: polkat]
#293063
04/19/09 07:19 PM
04/19/09 07:19 PM
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Joined: Jan 2003
Posts: 25,808
Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,808
Rio Linda, CA
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Before you go replacing parts at random, get a can of spray brake clean and clean the entire area, then take a flashlight and mirror to pinpoint the source of the leak.
If the leak is on the drivers side suspect one of the cooler lines or the shift shaft seal(s), if it's on the passenger side suspect the dipstick tube.
The INTERNET, the MISinformation superhighway
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Re: Odd 727 tranny leak!
[Re: John_Kunkel]
#293066
04/19/09 10:10 PM
04/19/09 10:10 PM
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Joined: Jan 2003
Posts: 15,367
Omaha Ne
TJP
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 15,367
Omaha Ne
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Quote:
Before you go replacing parts at random, get a can of spray brake clean and clean the entire area, then take a flashlight and mirror to pinpoint the source of the leak.
If the leak is on the drivers side suspect one of the cooler lines or the shift shaft seal(s), if it's on the passenger side suspect the dipstick tube.
And will add that sometimes fluid leaks originate in one place, drip down to the pan gasket upper lip, then run to the lowest point and DRIP. making one think it's the PAN GASKET, Wrong!!! As John said, clean, clean, clean, then wait for the drip. Trace it back to it's origin.
The key is have the entire area clean first. A couple of other problem areas that can lead one to suspect a pan or gasket are, The low/reverse band oring Ugly solution  , the Tailshaft bearing seal/gasket.
As said before clean it thoroughly, then look for the source. keep in mind the fluid does not go uphill. So once clean and dry, look for the source, maybe the pan gasket is wet but what is wet above it. Hope this makes sense
Tim
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Re: Odd 727 tranny leak!
[Re: TJP]
#293073
04/21/09 02:19 PM
04/21/09 02:19 PM
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Joined: Jun 2003
Posts: 190
Wilmington,NC
I go fast
member
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member
Joined: Jun 2003
Posts: 190
Wilmington,NC
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Quote:
Quote:
Yep! Does make sense, but as I said (didn't I?) I've cleaned it, and above the pan was dry everywhere. But I'll clean it again!
I just want to say that I myself got stung by a leaky servo cover (brand x) just 2 weeks ago. In spite of knowing and following the advice I gave you I missed the source of the leak 3 times. SHAME ON ME!!!!
It was a very small leak that would take 3 days to drop anything on the floor. In my defense HAHA it was in an obscure area. After 3 days it would leak enough to run down the the top side of the pan gasket all the way to the front, then around the corner and then drip off the pan corner on the opposite side of the trans.
Most common areas on a TF are
Gear shift selector seal LF
Kickdown lever seal LF
Line fitting LF
Neutral safety switch or gasket L side
rear line fitting LR side
Speedo cable LR. Note: has an inner and outer seal
Low reverse oring seal, middle-rear of main case below tailshaft housing and above pan gasket.This one is notorious for selling pan gaskets
rear bearing access cover (under trans mount)
Dipstick tube RF
I normally use brake clean and paper towels to clean thoroughly until there is no fluid anywhere especially above the pan. Then check every so often with a clean paper towel. once the towel turns pink, follow it back to the source. Sounds eassy right???? That's how I missed the servo cover leak 3 times. ARRRGGGHHHH Shame on me!!!!
Good luck and let us know
Tim
Most common,whether you know it or not,you just named every place a transmission could leak besides the front seal. 
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Re: Odd 727 tranny leak!
[Re: I go fast]
#293074
04/21/09 03:44 PM
04/21/09 03:44 PM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
I Live Here
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I Live Here
Joined: May 2003
Posts: 15,487
Florida
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I just changed a pan gasket last week and the rubber squeezed out just a little on the corner and had a leak R&R the pan dryed and installed anothe chep rubber gasket and used a 1/4 ratchet and by hand watching the gasket at the corners...no leak  often I will wash one with brake clean and dry with a air hose throw a hand ful of baby powder around the suspected area and wait for the leak the powder slows it down and marks the wet spot... 
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Re: Odd 727 tranny leak!
[Re: polkat]
#293077
04/21/09 09:29 PM
04/21/09 09:29 PM
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Joined: May 2003
Posts: 15,487
Florida
scratchnfotraction
I Live Here
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I Live Here
Joined: May 2003
Posts: 15,487
Florida
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IMO,yes that would be it you could try a BFH on it or another pan might want to get the newer pan gasket also,worth the 12-15 $ for it if you do..FYI..it does not compress and it will strip the bolt hole if over torqued usaly it will only pull half the threds out as the gasket is thicker you can use a longer bolt it that hole or heli coil it DAMHIK you can allways put a nice deep alum pan from summit on for 99$, good luck 
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