2015 2500HD Vibration and Shifting Problems

[WOODSTOCK]

My 2500HD dropped into first gear about two weeks ago.  Took it to dealer and they said no codes.  Shortly after noticed vibration.  Tires had 43,300 miles on them.  Put same exact tires on truck.  Still had vibration.  Took it to where I bought tires and they re-balanced them.  Still have vibration.  So it isn't tires.  Took it back to dealer.  The service manager told me it's a 2500HD and going to ride rough.....BS.  He felt vibration on ride with me.  Took him back to dealership and he told me to keep driving until it gets a code light.  He said they could not fix the problem.  He also told me he would not put it on a lift with vibration and shifting problem.  It now doesn't want to go into overdrive.  After talking to the service he fed me more BS, so I called GM and now have a case#.

[crankman]

When are you feeling vibration? Highway speeds? In town? How fast when you feel it?  Is it in the steering wheel or floorboard area the vibration.