cyclic drivetrain vibration

TCC- torque converter clutch.
Sometimes harmonic vibrations happen at certain rpm' and load on drivetrain so when you shift
into another gear it goes away or sometime gets worse.
So that's why I asked the questions. Now drive it and get into 3rd gear 45-55 and hold the vibration then flip the switch for lock up see what it does if it goes away lightly slow down to 45 and lightly accel up to 55 and see what it does?