I had a TCS (The Converter Shop) torque converter installed today. The transmission also recieved a slightly more comprehensive than soft rebuild on the trans. The flexplate was also replaced with a new hardened unit because we found that my stocker had hairline cracks in it.

Now the car has an extreme vibration when at freeway speeds. I actually noticed from the beginning that there was some vibration when on city streets, but the car feels as though it is going to completely shake apart when I'm on the freeway.

What could have gone wrong???

 

First I would rotate the driveshaft 180 degrees, if that don,t fix it then I would get in there unbolt the converter and spin it one third and rebolt it up.
It could be your driveshaft got dropped or dented during the install and may have to be replaced.
It could also be the converter itself was not balanced correctly.
I would try the easy stuff first.