Q: Torque converter vibrates - 2005 Chevrolet Avalanche 2500

The torque converter in my truck began to vibrate so I took it to the General Motors dealership. I was told that they felt something, but nothing was visible on the computer reading. They had me keep driving it in hopes that the engine light would come on. I proceeded to go too three different transmission specialists who explained that the torque converter was shuttering.

I returned to the first dealership where I was assured that was not the problem. I decided to have the torque converter replaced. They met me ½ way on the expense, fortunately. It seemed that the problem was fixed until the transmission completely went out around 1,000 miles later, after they had supposedly fixed it. In addition to that, the engine now has a tapping noise. I have been changing the oil every 3,000 miles. In your professional experience, what can I do to permanently solve this problem?