I had the transmission flushed a year or so ago.
They said it was pretty clean, including the new fluid and bottle of Lucas I'd added the night before!

It shifts nice and soft now. Upshift is fine.
It does NOT have the immediate downshift that it had before I heard the 'pop' noise and it started to exhibit the freewheeling feeling when I downshifted.
After that episode is when I added the fluid and additive.
The next morning I had the service done.
It still doesn't have the immediate downshift feature it always had up until a couple of days ago.

I suspected some kind of vacuum leak or faulty vacuum module, but I don't know anything about these transmissions.
I wondered about disconnecting the battery and starting everything over again, but I have no idea if that has anything to do with this problem as I perceive it.
The shop manager said there is a sensor that tells the computer you manually shifted, and perhaps that is what isn't working...

What I'm saying is this:
If you are going downhill in D and downshift to 2, it previously would downshift immediately and slow you down. Same if you then went down to 1.
NOW, it doesn't do that.

I experienced something like that going from OD down to D on the freeway, but around town it won't do it.
If you add throttle, you can tell you're in the next lower gear. If not, it sounds like it'* in D.
REALLY WEIRD.

What'* going on with this thing?

The 2nd gear band is toast.

I went back and had the manager test-drive the car and he confirmed it was doing exactly what I'd told him...no gear without more throttle, and no downshifting effect.

I can drive it for a while in 'D' and buy some time before getting it rebuilt for about $2200.

Guess I'll start thinking about building a long block next!