Any 727 experts have some advice?

Dartish said

This thing has me worried that its just gonna stop working on my way home from work today. Most everything I've owned has been equipped with a manual trans. I've installed several shift kits and done simple stuff to automatics, but I've never really been inside one

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I hate to tell you this , but it's very likely there is metal going through the valve body and/or governor causing the valves to stick.
There is almost no other explanation for shifts that late when nothing has changed since it worked fine.
If I were you I'd pull the pan and have a look, as it could save you some money.
(talking from years of trans building experience and not just an opinion)