I have a 2010 Chevy Suburban 1500 4WD with a vibration growl

6 months a go at 90,000 miles i had an issue where it felt as though i was driving over
a rough roads at sometimes when i would accelerate.   I had this in at a non gm
service facility and they said there was a shudder in the torque converter.  they
recommended a transmission fluid change in which they dropped the pan and drained
the fluid and then put new fluid in.  they said this may remedy the problem.  it
improved the the problem but I still get vibration after driving and i coast, i then am on
the gas pedal very lightly it gets a growl/vibration noise. i can feel this in the floor and
the steering column. there are also times but not every time when it goes into this
state that it feels like something will catch and the vehile will lurch.  THe problem
being described can be felt in town 10-25mph and up through 65 mph on the highway,
it also happens with the cruise engaged it has 97000 miles on it now and have been at
the GM dealer.  i have taken the technician for a ride and he feels what i am talking
about cant pinpoint what it is.  i have tries to pay attention to this in other vehicles and
the difference is that in mine the feeling is not smooth, rather like something isn't
functioning properly.  any help would be great.  thanks