A friend of mine has a 2016 GMC Sierra 1500 Denali with the 8-Speed transmission and the 5.3L engine. He had the clunk between 1st and 2nd gears and he took it to a dealership several times where they finally replaced the Servo Motor. He said that he hasn't had any clunks after that and it has been a few months since it has been done. I have a 2017 GMC Sierra 1500 SLT with the 8-speed transmission and 5.3L engine and I have been experiencing the clunk. Mine seems to happen more when the truck has been sitting for a while and I start it up and immediately take off. After the truck warms up, it doesn't do it quite as much. I haven't had a chance to take my truck back in the dealership to ask about the clunk and the Servo Motors. I have about 35,300 miles on my truck already, so it is still under warranty.