Torque Converter shudder: what does/did yours feel like? (2018 1500 5.3 6-speed, 120K)

I've been fairly sure for the last several months (based on forums) that I had the Chevy Shudder, I haven't been driving the truck since August. No CEL. It feels like a mild and intermittent cylinder misfire from 40-70mph, but I've been reading that it feels more like going on a rumble strip. Is there anything else it could be that might cause this without throwing a code?

Also: it crossed my mind that the slightly larger-than-OEM tires (285/65/r18) might also be a culprit. Any ideas?