I experience the same thing a high frequency vibration. It’s not at a severe level yet I was concerned. I took my truck into the local Chevy garage. The service manager said it was due the torque converter. He wanted to replace the fluid in the transmission. He said that might help. $675 later with new fluid the high frequency vibration comes and goes as before.
I’m planning a 2,000+ mile trip over Christmas. I’m concerned regarding possible transmission failure on the trip. The truck is a 4 door with a 5.3 liter engine - 4x4 of course. The truck has 130,000 plus miles on it.