727 Leak Inside Bellhousing

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71GSSDemon

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So, looking at the trans, the input seal looks perfect and still has some greese present. I did see this pipe plug looking like it was loose. I checked a spare trans and this plug is flush. I took it out, cleaned off the Teflon tape, used pipe paste and reinstalled. Now it went flush. Could it be the source of the leak?

20210509_205333~2.jpg
 
These Leaky Transmission's are hard to determine. How did you know for sure it was coming from the Bell Housing?
 
These Leaky Transmission's are hard to determine. How did you know for sure it was coming from the Bell Housing?

I don't have an inspection cover right now and you can watch it drip from inside the bell. Also, reaching in the best you can, you can feel that is puddled there. I removed the trans last night and the whole inside of the bell is wet with fluid. The front seal has about 100 miles on it, looks perfect and still has some grease on the edge. The torque converter seal surface looks smooth also, with no grooves.
 
Here are before and after pics of the questionable pipe plug. Before, while still in the car. And after, resealing and reinstalling it and tightening it.

upload_2021-5-10_7-3-55.png
 
Could be, or you clipped the front pump O-ring when you installed the pump. Also make sure you have good gaskets on all of the front pump bolts.
 
Could be, or you clipped the front pump O-ring when you installed the pump. Also make sure you have good gaskets on all of the front pump bolts.

I didn't rebuild the trans, but it doesn't mean someone else didn't do just that. It came out of a working car; it is all I know about it. I installed a manual valve body and new front seal, but that is it. I will double check the pump bolts.
 
I believe that pipe plug is for access to the kick down apply lever pivot shaft. Yes it needs to be sealed and tightened properly. Also, all the pump bolts should have had new sealing washers under the heads. Some rebuilders use a dab of silicone on the pump bolts just to be sure the bolts are sealed for sure.
 
did you change the converter? Could be leaking there. Drain plug, welded lugs, or if it’s welded together.

yes that plug will leak and it was loose so you fixed a problem there.

Using sealer on the pump bolts threads is useless. The bolts go into blind holes. So that’s why they have the washers on them.
 
If you overfill a TF it will blow the excess oil out the vent at the top of the pump, until it finds it's working level; then it will stop.
At this point, with the trans down, it would be hard to air-pressure test it, but I would figure out a way to do it, cuz I hate to do things twice.

904s like to split the convertor snout starting in a corner of the pump-drive slots. Usually this is obvious when you pull it out, but not always.
 
It shows "add a pint" on the dipstick so it isn't overfull and still drips fairly steady. The converter was changed. It doesn't appear to have any visual issues.
 
A steady drip is a big problem. Something like the converter body/hub will just coat the inside of the bellhousing. How do you track that down?
ATF is harder to find the leak because it’s so thin.
 
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A steady drip is a big problem. Something like the converter body/hub will just coat the inside of the bellhousing. How do you track that down?
ATF is harder to find the leak because it’s so thin.

It steady drips (drips every few seconds and time increases between drips the longer it sits) for a period of time after shutting down. It likely leaks while running too, but hard to know that as it is slung all over. It seems to leak to about a 4" puddle, but ATF is so thin, it it hard to determine exactly the volume. Should have put a container under it to check. It doesn't seem to leak more whether it is a couple hours or couple days. It makes me believe it is hot fluid or splash/pressure area.

Yes, the whole inside of the bell is wet, so the converter, wind, rotation is throwing it all over. The rake of the car is likely why it drips from where it was pooling in the bell.
 
I have seen hairline cracks in the front pump do that. Pull the pump and look it over real good. Look close at the bolt holes. I had one that had a crack going into one of the bolts that held the pump in. It would only leak when the car was running.
 
So, looking at the trans, the input seal looks perfect and still has some greese present. I did see this pipe plug looking like it was loose. I checked a spare trans and this plug is flush. I took it out, cleaned off the Teflon tape, used pipe paste and reinstalled. Now it went flush. Could it be the source of the leak?

I had a very small leak at that plug. I’m not sure what it’s purpose is but after doing what you mentioned it never leaked again and has been working fine for two years.
 
It steady drips (drips every few seconds and time increases between drips the longer it sits) for a period of time after shutting down. It likely leaks while running too, but hard to know that as it is slung all over. It seems to leak to about a 4" puddle, but ATF is so thin, it it hard to determine exactly the volume. Should have put a container under it to check. It doesn't seem to leak more whether it is a couple hours or couple days. It makes me believe it is hot fluid or splash/pressure area.

Yes, the whole inside of the bell is wet, so the converter, wind, rotation is throwing it all over. The rake of the car is likely why it drips from where it was pooling in the bell.
Is the converter new?
 
It shows "add a pint" on the dipstick
Is that hot/cold, park/neutral, running/or not,and on level ground. Normally the trans has a 1 to 2 degree tail-down angle.
Are the stick and tube a matched set and is the stopper on the end correctly anchored?
The trick is to not have the sunshell, or any other spinning parts flinging oil.
As the trans cools off, the oil and air inside, contract, and the unit pulls in air as it stabilizes. Then as the unit heats next time out, the oil and air expand. The air vacates thru the vent, sometimes, if the oil is being aerated,that vacating air will take oil with it. The vent is baffled inside the trans ( or was when it left the factory), or it had a labyrinth separator, but it can only do so much.
I'm not saying your leak is the vent, only the vent, and nothing but the vent, lol. What I am saying, is; just cuz the stick says whatever, doesn't necessarily make it so.

my biggest question was the pipe plug that seemed looser than it should be.
Pipe plugs have to be tight to seal. But again, because they are tapered and a high-rate of leverage screw, which is a ramp, so; it can be easy to overtighten them. Your teflon-tape fix should be fine.
 
Is that hot/cold, park/neutral, running/or not,and on level ground. Normally the trans has a 1 to 2 degree tail-down angle.
Are the stick and tube a matched set and is the stopper on the end correctly anchored?
The trick is to not have the sunshell, or any other spinning parts flinging oil.
As the trans cools off, the oil and air inside, contract, and the unit pulls in air as it stabilizes. Then as the unit heats next time out, the oil and air expand. The air vacates thru the vent, sometimes, if the oil is being aerated,that vacating air will take oil with it. The vent is baffled inside the trans ( or was when it left the factory), or it had a labyrinth separator, but it can only do so much.
I'm not saying your leak is the vent, only the vent, and nothing but the vent, lol. What I am saying, is; just cuz the stick says whatever, doesn't necessarily make it so.


Pipe plugs have to be tight to seal. But again, because they are tapered and a high-rate of leverage screw, which is a ramp, so; it can be easy to overtighten them. Your teflon-tape fix should be fine.


That was at operating temp, level ground, with a matched dipstick and tube and in Neutral. I checked the dipstick and tube to make sure where matched before pulling the car apart. Yes pipe plugs are tapered, but also very easily leak if not tight. There was Teflon tape, I reinstalled with Teflon paste as I typically have better results. Loctite 567 is a good one. Thank you for your input, everything is welcome.
 
Another observation. The balloon side of the converter was dry. The inside of the bell was wet. This leads me to believe, the plug was indeed leaking, the ring gear blew the ATF around due to fanning effect. The dripping was just until all the ATF that accumulated in the bell leaked out. Also, the fanning of the converter/ring gear, could draw a vacuum on the plug???? I have seen this time of effect on outboard marine engines where the flywheel can pull an oil leak from a lower location up to the top and give the appearance of a different source of the leak. Just thinking here....
 
I would checking the pump O ring as u have oil at the bottom of the pump at the case. Looks like a trail from the pump to the bottom of the bell. The fiver washer behind the bolts could be leaking. Kim
 
man that really sucks having done all that work,and having to pull it out again.i hope you find the source of your leak.
 
Here are 3 pics as taken last night looking thru the inspection cover opening. Looks dry at the seam for the pump. No real fluid until the bottom where it is pooling. Coming back out on Friday.

Trans Leak Center.jpg


Trans Leak Drivers Side.jpg


Trans Leak Passengers Side.jpg
 
From the looks of the last picture, the pipe plug is no longer leaking. Since you are going to have it out & apart again, I'd change the pump o ring & the converter seal, being very careful during installation.
 
I have overfilled my trany several times because the fluid is so hard to see on the dipstick. And I have to look at both sides of the stick... one side will be dry and the other show overfull if do it to quickly .
 
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