My 2018 Terrain has AWD and while driving in a state park up a hill, I decided to switch to AWD from 2WD (front wheel drive). I was used to the switch on two previous Silverados I previously owned, while moving at about 5 MPH. I used to make the switch on my Silverados that way. However the Silverados were RWD and evidently switching to AWD on a Terrain works differently. Thinking there was a problem, I went to the GMC dealer to check this out. The Service Advisor told me to bring the car to a stop and just turn the AWD/2WD switch until it hits the stop and then release the switch. Well that does work, but interestingly, those instructions were NOT in the owners manual. At least I didn't see it.