727 Question

Posted By: moparmike1

727 Question - 12/12/12 06:28 PM

I have a 1972 727, stock except for a Transgo TF-2 kit. It was rebuilt last winter, developed a small leak in the spring once I began driving the car, that was either the vent or input shaft seal.

Transmission has been out, input shaft seal and bushing replaced, still leaking. Confirmed to be the vent but it has the right amount of fluid in it, drained converter and filled from empty.

Does anyone know what can cause enough pressure, in park, for fluid to come out the vent? Car is on a level surface.

At this point, we are absolutely sure of:

1. Fluid is not overfilled.
2. Leak is from the vent, not the converter hub or input shaft seal.

Thanks in advance,

Mike.

Posted By: dOoC

Re: 727 Question - 12/12/12 06:40 PM

I have done myshare of TF in my day ...and I have never seen a vent-leak uNless the trans was not waaaay overfilled. If it "developed" a leak .. then it is more than likely the "fit" of the front seal. Have you checked this "fit" ?

Posted By: moparmike1

Re: 727 Question - 12/12/12 06:47 PM

Quote:

I have done myshare of TF in my day ...and I have never seen a vent-leak uNless the trans was not waaaay overfilled. If it "developed" a leak .. then it is more than likely the "fit" of the front seal. Have you checked this "fit" ?

The seal fits fine, leak is definitely the vent.

Thanks,

Mike.

Posted By: dOoC

Re: 727 Question - 12/12/12 08:22 PM

How did you check "fitment" ? .. and it can not "leak" out of the vent(uNless the trans is way overfilled)... it has to be BLOWN OUT of the vent ...and how would you think that might happen?

Posted By: moparmike1

Re: 727 Question - 12/12/12 08:48 PM

Quote:

How did you check "fitment" ?

Installer said the seal and how the converter meets it are fine. The fluid is definitely from the vent.

Quote:

.. and it can not "leak" out of the vent(uNless the trans is way overfilled)... it has to be BLOWN OUT of the vent ...and how would you think that might happen?

That's my question, what can cause the fluid to be blown out of the vent?

I'm going to the shop later today and will update this thread with anything else they've found.

Thanks,

Mike.

Posted By: moparmike1

Re: 727 Question - 12/13/12 02:48 AM

btt for the evening crew.

Mike.

Posted By: superwrench

Re: 727 Question - 12/13/12 02:59 AM

Three things cause fluid to burp out the vent.....Way too full, way too hot, or sudden decel forces fluid up front to the pump area.
I used to have the vent leak when drag racing on a real short track with a "real" short shutdown which required LOTS of brakes.
Did you guys use new sealing washers on the pump bolts? I've had a few leaks from around those before.
Otherwise the only place it's gonna leak is from the convertor seal/bushing, or the oring around the pump. Not much else left.....

Posted By: dOoC

Re: 727 Question - 12/13/12 09:35 AM

..... OR it could be a newly BENT or cracked hub on the converter.

The burping or barfing out the vent ? ... that is a severe and monsterous "leak"....

I would AGAIN check the seal ...and see if there is that little spring in there. I have seen cases where THAT is missing ... even in new seals.