Adding a vent on a 727

I never saw a vent on an automatic. You have other issues, Maybe try another dipstick first. I have seen the dipstick rubber bad from age. Could be internal pressure leak. I had a truck do this it was a broken lip seal internally.

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I have read articles on hi h.p. , hi rpm drag cars running trans vents w/ a filter on them up high /even in the interior or trunk.