This has happened a few times now and I'm not sure if it's normal. My truck has 22k on it. Sometimes when I'm driving, I hit the gas and the truck refuses to move. It feels as if the parking brake is on when it's not. Only happens after the truck has stopped. Yesterday, I was coming up to a stop light. I stopped fully on an incline. I left the transmission in drive, no parking brake. When the light turned green, I hit the gas but the truck didn't move. I gave it a little more gas and nothing. Finally I felt something engage and the truck bucked forward a little. I've never experienced this on any other vehicles I've ever owned. Thoughts.