My truck vibrates with a kind of droning harmonic repetative cycling rumble when in park. I'm concerned its in the transmission. I just replaced the U joints because it vibrated badly going down the road. That fixed the vibration while moving. While I was under there I grabbed hold of the splined output shaft from the transmission. I shook it and found it to have some play in it. Maybe 1/16th of an inch. Is that excessive? I just don't know the history of this truck. Could the vibration be the torque converter? I don't want to get into the cost of rebuilding it. I'm on the fence about just selling the truck. I have an opportunity for another C6 but it has a transfer case attached. Can I just unbolt the transfer case so it will work with my 2 wheel drive? It will bolt up to my motor. I know this is a lot of questions but Im trying to decide what to do. Thank you in advance. Eric.

 

Take the belt off, try it. Inspect the harmonic balancer.