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cambo 04-29-2008 11:32 PM

66 c4 transmission breather ?
I have a 66, Coupe 6 cyl with a c4 in it. I just got it and the transmission leaks on the ground when not running. I have the equipment and parts to change the pan gasket and filter. However when i crawled under i noticed a tube just hanging down. This tube runs from the carbrator air breather down to the tranny ? I think. It is metal with a rubber hose on the end. Now my guess is this attaches to the vent on the tranny or a vacuum tube or somewhere. But I cannot figure out where this is or where this tube should go. Anyone have any idea? I have read on other posts that fluid can run out of the vent in some C4's The leak I have is so significant that the tranny always shows empty of fluid if left for a day or 2.

Let me know what you think.

blue66mustang 04-30-2008 09:08 AM

RE: 66 c4 transmission breather ?
The tube probably is supposed to go to the vacuum modulator on the rear of the Trans. This uses manifold vacuum verses governorpressure to tell the Trans when to shift. There is also a case vent tubeon the drivers side above the shift linkage.

LPlum 04-30-2008 10:27 AM

RE: 66 c4 transmission breather ?
My 66 has the same leak. I have changed various seals and pan gasket, and still leaks. I have narrowed it down to the tranny dip stick/filler tube o-ring or the front pump seal. If it's the front pump seal the tranny has to come out, and be taken apart. If I do that it should just be rebuilt/overhauled.
Let me know if you figure out what the leak is.

cambo 04-30-2008 10:08 PM

RE: 66 c4 transmission breather ?
Thanks for both your inputs I am crawling back under her on saturday. I am going to check out all those ideas and see. I also got a idea from a friend to fill it up and run it while I am under it just to see if i see any drips or leaks or bubbles etc. I'll let you know.

cambo 05-07-2008 11:16 PM

RE: 66 c4 transmission breather ?
Well I finally got under her, and cleaned up the bottom of the tranny. After trying to take off the pan i realized some one tried to solve the problem with silicone. and didn't know what they are doing. After some fenessing it seems like it is now down to a very small leak that I can live with coming out what I would call the shifter shaft. I saw another post regarding this and it surmised that this seal could be fixed readily enough without dropping the tranny at a tranmission shop. After getting it back on the ground I have noticed 2 things. First that it won't shift out of low. at all. and second once the RPMS get above about 2500 it makes a really nasty sounding rattle or vibration noise. Both in park and driving.. The shifting I think is from the breather/vacuum tube and I have ordered a haynes manual in hopes they can spell out where that tube goes because I still can't figure it out. I will post again when I get the manual and hopefully solve the shifting problem. As for the rattle/ vibration it back in the engine. Like last 2 cylinders or transmission I am thinking of checking the starter/muffler/bell housing/ring gear. Anyone have anything similar?

Hot Pony 12-10-2013 10:21 AM

Thanks everyone, this has been helpful to me. I am having a similar issue.

1970 12-11-2013 08:34 AM

the vacuum line goes to a modulator on the back of the trann ce=c&&cagpspn=pla&gclid=CMjB1u-jqLsCFcpDMgodFFkADgy also when c4s sit the fluid drains out of the torque converters and they leak out the breather and if the vacuum line isn't hooked up to the tranny then you have a leak and that should be affecting how your engine is running

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