Wanted to throw in a update on my 2014 silverado, my truck has always had that issue with the drive train knocking when slowing down, multiple times GM had looked at it and stated it was normal, at 87k miles the dealer replaced the torque converter, transmission mount and rear pinion seal. Now last week it did it again however for the first time a grinding sound followed and it began to do the same knock when accelerating, took it into my local Chevy dealer, at 92900 miles and with 26 days left on my power train warranty they are telling me the transmission has damage and needs repairs, ill keep you all posted with exactly what it is that they are replacing, im glad I also have extended warranty after my factory warranty expires, now im enjoying a 2019 LTZ for the mean time.