Alrighty then, here's the update at the end of day three. He told me after installing a new Torque Converter it still makes the same sound. So frustrated again he calls his "hotline" tech. The tech suggests it's the valve body. Say what? As far as I know the valve body doesn't do anything when it's in Park right? It only shifts the gears through passages and solenoid valves. So now he's got his builder putting together a whole different transmission. We'll never see our Yukon again! Of course his incentive is his newer Denali XL that's been sitting in our driveway for 3 days.....