Vibration in 2nd gear - A/T

I found a few threads about this but none had a resolution, hopefully there was one and someone can provide a link.

The truck just passed 200K. I'm not behind, or even near on any scheduled maintenance including a/t fluid flush. Tires good & balanced, alignment good, etc.

The vibration is also there if you manually shift from L to 2. Goes away if you manually shift into 3.

I tried this in 4WD and I think I still felt some vibration, but definitely less.

 

Does the vibration occur at certain speeds, all speeds while manually shifted into 2, at idle when shifted into 2?

Any further description of the vibration? Where you think it's coming from or what it's like? I know it's hard to describe in words on the internet, but the more details the better (though still a longshot).

When was the last fluid and/or filter change? Did you do it, did a dealer do it?

Did anything else recently change that could be related? Or has this been a progressive issue over a long period of time?