I have a 6.0 lt with a automatic with a vibration in overdrive on highway

I found a sealon the shaft going into the torque convertor was cracked. replaced it and it took care of about 90% of the problem. I had to drop the trany regardless. :-<

Thank you and sorry for the slow reply. Mine is an 8.1 litre and my vibration seems to be from a misfire due to a sensor. There's been a recall on the ckp but not for my motor. It vibrates during idle after but only after warming up and during driving. Still trying to find the exact origin of the vibration. Glad yours is working better.