2005 Ford Escape XLT

Have a bad vibration when car gets to about 40 mph, when the overdrive is taken off, the vibration diminishes but doesn’t completely go away.  Motor mounts and transmission mounts have been replaced.  Have had numerous people look at it and someone suggested going to Ford and asking for a transmission additive for a torque converter vibration??…..  Is this just added to the fluid or does the trans fluid have to be drained and replaced?