A bit old, but any chance you can fix this video link? I’m having a vibration exactly as OP describes. It’s even persisted to a completely new engine. One thing i can add is that i have a 46rh. Once i click overdrive the vibration comes down a decent amount. Problem has persisted since the previous engine with a 727 trans and different converter and different tires. Car just went through a complete rebuild, but the only things i haven’t checked are the front u joint, and if the wheels themselves are out of round. I had the tires professionally balanced. They didn’t let me know about any potential wobbles in the wheel but they could’ve missed it i guess. I checked pinion angle once but probably wouldn’t hurt to check again.