I had an issue with the OD on one of my vans that may or may not be of a similar nature:
When it shifted in or out of OD on the highway, there would be a shudder that felt exactly like I was going over a rumble strip. At first I thought that's what it was, but soon realized that there were no road features that corresponded with the noise, and figured out that it happened when the trans shifted.
I drained the transmission (about 3 of the 6 qts drained out) and replaced it with new fluid. The problem vanished.
Moral: Automatic transmission fluid loses its magic properties in time. If it hasn't been replaced recently, or - more likely - you don't know when it was changed, do so.
I also changed the filter and replaced the pan gasket, but there were no shavings or anything so I don't regard this as having been part of the fix. Just refreshing the fluid did the job.

I figure that I have 50% new fluid now. If drained and refilled it again, I'd be up to 75%. I sold that van, though....