Shamrock, this is your 3rd torque tube replacement???
a similar issue happened to me 3 months ago, noise while idling and had the torque tube replaced.
THIS WEEK, the car DIED after accelerating from a stop sign - DEAD in the middle of the intersection!!! NO power, NOTHING! cell phone was behind the up/down screen-stuck in the car! NO onstar! used the lever release on the floor to get the car door to open! Got lots of help from people googling over the car - they called the chevy dealer and got it towed(stuck in park-dragged it up on the flatbed tow). A master fuse blew, but they are still trying to diagnose what killed all power!! --- I have seen posts here where the torque drive issue caused the MAIN CRANK to go "a hair" out of alignment - causing starting/running issues... a NEW 6.2 might be the solution?!?!?!
