I have a 2009 G8 GT, just put in a rebuilt transmission and coan triple disk converter 2 weeks ago. Today I got in the car and took off and it started bucking pretty bad so I turned around, pulled back in the parking lot and tried to stop and the trans felt like the converter was locked and tried to pull as i was stopping and then died as i got it stopped. Now whenever I put it in gear, forward or reverse it jerks and dies. Every now and then I can get it to stay running for a few seconds in gear but have to hold with brake pedal with everything I've got until it dies, the rpm aren't raising just feels like the converted has not slip at all, any ideas?

 

Sounds like the lockup clutch in the converter is engaged.
It could be an electrical problem or the converter has gone bad.

 

Sounds like the converter is staying locked. Could be a converter or trans issue. I've seen the tcc regulator valve in the pump cover stick causing this issue multiple times.

You can try getting the car moving and cycling the tcc on and off with a scan tool possibly free the valve. Good luck.