1999 Suburban shifts late / high rpm

[PapaHepcat]

We were on the way home from camping today (not towing) when my Suburban seemed to start shifting late. It was fine on the way out and about halfway back. We went through a drive-through to get something to eat, when it started happening. I never shut it off the whole way home. And if I ease off on the gas, it'll shift.

A couple of notes:
While sitting in the drive-though line, I noticed a slight, occasional stumble while idling in line. Related?

Tranny fluid is relatively new. It was serviced not long ago. The shop dropped the pan went through it and said the tranny was in pristine condition. No shavings or anything, so they just refilled it.

 

[zora]

Did you check the transmission fluid level after the problem occurred?
Do you have a check engine light on?

 

[PapaHepcat]

No check engine light, and I haven't checked transmission fluid level yet. I was pretty beat yesterday.

Drove it to work again this morning to test more, and everything seems to be shifting fine. I'm not sure what would cause it to delay yesterday, but be okay today