I've searched for this and couldn't quite find what I have going on, so apologies in advance if I missed something.

The 2-3 shift in my 67 Coronet's 727 has become kind of slow under heavier throttle. It doesn't flare, it doesn't hang, it just kind of sliiiiides from 2nd to 3rd over maybe a second or a second and a half. 1-2 is fine, and 2-3 doesn't feel strange when I'm driving like a normal person.

I last had the pan off about 5 years ago to throw in a B&M 10226 kit and did all of the band adjustments you usually do when you have the valve body off. Not entirely sure how many miles have passed since then, probably around 10k at most.

I have a Lokar-type cable instead of the old linkage - it is adjusted out to have full pressure at WOT.

I couldn't find anyone describing this particular behavior, only people with shift flares or with this behavior only when the trans is cold.

Should I just start with a fluid change (it's not a ton of miles, but it is old) or a filter/full band adjustment again, or am I more likely nearing the end of some friction material's life?