2011 SR5 - truck vibrating

Hey everyone, hoping someone here might have some insight. I’ve been dealing with a weird vibration issue on my 2011 Tundra SR5 4.6L (currently sitting at around 180,000 km), and it’s been going on for about three months now. It’s not crazy intense, but it’s definitely getting worse little by little, and it’s starting to drive me a bit nuts.

The best way I can describe it is like that feeling when you’re driving over rough pavement or those rumble strips on the shoulder of the highway, except I’m on a smooth road. What’s strange is that I don't feel it through the steering wheel, gas pedal, or brakes. It just feels like the whole truck is buzzing lightly, like it’s coming through the body.

It almost always happens around 60 km/h while cruising. It'll last a second or two, and sometimes I can make it stick around a bit longer if I keep steady pressure on the gas. But if I tap the brake or slightly touch the gas again, it disappears instantly. Super odd, and super consistent.

I’ve already gone ahead and replaced the U-joints and the center driveshaft bearing (hanger bearing), but unfortunately, that didn’t fix it. I’ve been scratching my head ever since. No obvious issues with the tires, and I haven’t done any recent suspension work. The truck otherwise drives fine, no warning lights or codes.

I’m honestly at a bit of a loss now. I’m starting to wonder if it could be something like a driveline angle issue, engine or transmission mounts, or even something internal in the trans or torque converter. Just not sure what direction to go in from here.

Has anyone experienced anything like this before? Any advice or things I should check would be really appreciated. Just trying to get ahead of it before it turns into something worse. Thanks in advance!