When backing up and in reverse I hear noise like a quick clunk and you can feel a slight jerk but it does stay in reverse. It doesn't do this all the time! Andy ideas?
How new is the vehicle? Is the vehicle cold (just started) causing the idle to be higher? I noticed my 2016 runs so much smoother after I took it out for about a 150 mile country run that involved some full throttle acceleration. Also, the CVs can make some noise when shifting from park to drive to reverse etc.
There is a Transmission SW update that should fix the problem. Most Transmission problems should be SW related, any HW Related Transmission problem would also impact GM vehicles too because the transmission is co-built with GM with SW being the only difference between them.