Has any one successfully changed out a rod without pulling the motor?
2006 A8L with 4.2L rod 7 snapped Bore is good so is crankshaft.
Cause is very mysterious but the rod snapped at very low speed seconds after it was started.

 

Not possible. You would have to pull the head so you can get the piston out of the top in order to change the rod. I also highly doubt your connecting rod journal is untouched...
In some engines it is possible to pull certain pistons out of the bottom of the engine, but then that would necessitate removing the crankshaft out of the way, which means pulling the trans away and taking out the bottom end of the block... In which case, even if possible, it would be easier just to pull the motor out and do it the proper way.
Also, in your case, it might be cheaper to just get a replacement engine depending on the extend of the damage the rod did, keep in mind it might have scored the cylinder walls.