Sorry Marshall, but the oil level in the trans will never get high enough to come out the vent. A clogged vent will make the trans hard to fill, and it is there for expansion as you said. The vent is located on the top edge of the output shaft support on the PF and TF. On the 727, it is in the front pump up towards the top. John Grady had a good reply on what happens in the converter when it drains back. The only positive seal there is the front pump seal. Air can enter from inside the trans in a number of ways. The drive sleeve has an O-ring on one end, but a steel ring on the other. You also have a metal to metal contact between the pump and regulator housing. The input shaft going into the converter also has steel rings with a small gap. When everything is tight and perfect, drain back will be minimal, but air will still displace the fluid eventually. The external seals are usually good enough to keep the fluid where it belongs, but any wear on the throttle shaft or shift cable housing can be a leak point.
More on this at the Spring meet transmission seminar.
I believe all transmissions have a vent that serves the same function as the vented caps on the power steering pump and the fuel tank. The vent is located considerably above the design oil level in the case. If there were not a vent the expansion of the oil as it warms would push it past even perfect seals and surfaces. Conversely, a clogged vent will cause exactly that to happen.
If the seals and/or sealing surfaces for the Torque Converter are worn they will allow the fluid to return to the case and it will drain from the vent and somewhere on the upper case will be wet with fluid which eventually finds it way to your floor.
The cure is obviously good seals, non grooved sealing surfaces, and over boring and re bushing the pivot points which requires tear down and machining. That may include the converter.
On Thu, Dec 22, 2016 at 2:03 PM, 'Rich Barber' c300@xxxxxxx [Chrysler300] <Chrysler300-noreply@xxxxxxxxxxxxxxx> wrote:
Posted by: <dverity@xxxxxxxxxxx>
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