Engine Vibration 3k RPM

if you can verify it isnt a misfire, Id say its your rotating mass. i had a similar problem and it was a defective pressure plate.yes I know yours is auto but I m just saying it sounds similar. Mine was so bad the dash rattles sitting still

you may have to try a new converter etc. I had pulled my trans more than once figuring mine out...you could try a balancer first etc.