GreenZ98
I'm Awesome
My 06 was doing the same between 56-58 mph. Ended up being the torque converter. I could get to the speed the shudder started at and lightly touch the brakes without letting off the accelerator and it would clear up instantly. Poured a 2oz tube of lubgard shudder fix in just to be sure the touching the brakes thing wasn't a fluke and sure enough it completely quit doing it so then I knew for sure it was the torque converter.