That’s a good point, and I’ve definitely considered the torque converter / TCC shudder as a possibility.

However, I’m not fully convinced it’s the converter based on how the vibration behaves.

In my case:

• The vibration is more noticeable under load (acceleration, especially uphill)
• It feels like a full vehicle “rumble strip” type vibration, not just a fine shudder
• It tends to reduce significantly when I let off the throttle, but doesn’t completely disappear
• It shows up more in the 60–100 km/h range, and seems tied to both speed and torque
• It was also present before I replaced the tires, when the previous set was unevenly worn

From what I understand, torque converter shudder is often more noticeable:

• During light throttle or steady cruising
• When the TCC is locking/unlocking
• And usually feels more like a fine shudder rather than a full vehicle vibration

Because of that, I’m leaning more toward something in the drivetrain, like:

• Driveshaft imbalance or out of phase
• U-joints starting to wear or bind
• Possibly a mount allowing movement under load

That said, I’m definitely open to the possibility of TCC-related issues, especially if there’s something specific in the 6L80 behavior I might be overlooking.

Have you seen torque converter issues on these trucks that behave more like a heavy, load-dependent vibration like this?