Hi Scotty,

I have a 2013 GMC Sierra 1500 5.3L with 60k miles.

When I shift the transmission into reverse or drive I hear a quick ticking noise (one or two quick clicks). I also hear this same quick tick noise when it shifts into 2nd gear. I had the U-joint checked out and it's ok, any idea what it could be?

driv shafts on those often do that where they slip into the yoke, a known flaw. As long as U joints are good, don't worry about it.