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727 Transmission Leak!!!

GTXGreasemonkey

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I've been chasing a leak coming from inside the bell housing area for a month now. I'm on the verge of removing the trans for the fifth time. Here's what's been done so far:

- Replaced front pump seal around the main shaft
- Ensured front pump mount bolts were torqued
- Verified trans is not being overserviced. It's never leaked from the vent hole
- Sent transmission back to the builder who opened up and replaced everything again. All seals and the front bushing the converter rides on
- Still leaked so I then sent the converter to the shop and had them inspect and replace the stub shaft

Each of these steps have been progressive as i've installed and had it leaking each time. I currently have everything brand new installed and it's still leaking. Key notes:
- I don't notice much if any leak while it's running. It usually takes about an hour until i then notice a few inch pool forming under the trans. I believe it's always leaking, but only notice it when it's sitting for a while, and it's allowed to run out of the bell housing.

My transmission builder had me stop running the Dexron II fluid and filled it with Type F. He believed the synthetic was too thin for the seals to properly seal. That's proven to not matter at all.

What else could this be? Do I need to find another housing and transfer everything into that trans to just start over?
 
Obvious not the same transmission, but I had a Fordomatic in my 57 Retractable that wouldn't stop leaking until I put washers on the front pump retaining bolts. Not sure how the fluid got there, but the washers stopped the leak.
 
It is not easy at this point, but did you dial in the trans housing to the crank? Making sure the housing is concentric to the cfank.
 
Hmm... i know it's crazy... but is there a crack in the torque converter?
^^^^

I remember 2 oddball leaks like that. 1 turned out to be a Crack at the hub weld, ( but you said that was redone) and the weirder one I never found until this particular converter was laying on the bench, leaking :realcrazy:

Turns out 1 of the flexplate lugs had developed a crack.
 
I've been chasing a leak coming from inside the bell housing area for a month now. I'm on the verge of removing the trans for the fifth time. Here's what's been done so far:

- Replaced front pump seal around the main shaft
- Ensured front pump mount bolts were torqued
- Verified trans is not being overserviced. It's never leaked from the vent hole
- Sent transmission back to the builder who opened up and replaced everything again. All seals and the front bushing the converter rides on
- Still leaked so I then sent the converter to the shop and had them inspect and replace the stub shaft

Each of these steps have been progressive as i've installed and had it leaking each time. I currently have everything brand new installed and it's still leaking. Key notes:
- I don't notice much if any leak while it's running. It usually takes about an hour until i then notice a few inch pool forming under the trans. I believe it's always leaking, but only notice it when it's sitting for a while, and it's allowed to run out of the bell housing.

My transmission builder had me stop running the Dexron II fluid and filled it with Type F. He believed the synthetic was too thin for the seals to properly seal. That's proven to not matter at all.

What else could this be? Do I need to find another housing and transfer everything into that trans to just start over?
Does it continue to leak after sitting? Do you then dry it off and after a while is it still leaking?
 
It is not easy at this point, but did you dial in the trans housing to the crank? Making sure the housing is concentric to the cfank.
I didn't build the trans. I can verify this with the builder, but I'd expect him to claim that it is. He is a "specialist" who came highly recommended. I know mistakes happen.
 
Yes. It tends to leak as it sits. Even after being whiped down it'll come back slowly.
What I would do is first after the car has sat a couple days check the fluid [engine not running] and mark the stick, remove the transmission. On the bench, remove converter, cap cooling line ports, install drive shaft or a slip yoke, install dipstick tube. Wash pump area and dry. Add several quarts of fluid to raise the level in the transmission to the level you marked on the stick.. This is what the converter drain back does when sitting. With the raised level you should eventually see fluid leaking. This is what I would do.
 
What I would do is first after the car has sat a couple days check the fluid [engine not running] and mark the stick, remove the transmission. On the bench, remove converter, cap cooling line ports, install drive shaft or a slip yoke, install dipstick tube. Wash pump area and dry. Add several quarts of fluid to raise the level in the transmission to the level you marked on the stick.. This is what the converter drain back does when sitting. With the raised level you should eventually see fluid leaking. This is what I would do.
Not a bad idea at all. When I get it out i'll try this!! Thanks
 
Not a bad idea at all. When I get it out i'll try this!! Thanks
Let me know how it turns out. You can also fill the converter and cap the hub. Dry it well and prop it up in the running position. Watch it closely and rotate it if nothing shows.
 
Update:
The transmission builder has had it, and nothing has jumped out as being wrong with the transmission. He did take a look at the converter I just had the stub shaft replaced on and that appears to be cracked. As you'd expect i'm not happy considering I had them "repair the shaft", and then I specifically asked the shop if the pressure/leak checked the component and they stated that they did. I'm having the transmission put back together now, and i'm debating having the shop properly repair or just order a new one. I'm leaning toward replacing and then taking this to them and holding them accountable for a proper repair to keep as a spare. I should have everything back together this weekend so i'll keep you posted.
 
i thought torquefiltes were supposed to leak? seriously, glad you found the problem and i learn something constantly from messing with these things.
 
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