push button trans. leaks by cable

The stock O-ring in a crappy buna type. That's your only seal. poor design. After replacing an o-ring TWICE and going through the shift/adjust drill (still never had it spot-on).....I went to the HELP section of the local autozone. I bought a kit of ureathane (possibly metric) o-rings. They had a 50% thicker wall. Maybe they were AC o-rings?
I don't remember exactly.

Anyway...use a thicker O-ring, and it will seal tighter with the housing. the problem is after 40+ years, the steel (threaded) part slightly eggs out the alum. bore in the trans housing. A skimpy OEM O-ring doens't do the job.