I've got a 2000 gmc Yukon. Lately I've noticed that the rpms will go up 5 or 6 hundred while shifting in between 2nd and 3rd. The other day under half throttle it jumped from around 2 Grand to close to 5 grand before I quickly noticed it and got off the gas. It was like driving a stick and pushing the clutch in while staying on the gas. I have also noticed that a few times lately when I start it the tow/haul light is on. Without me pushing it. I'm not sure if it is related but the service engine light has came on a couple times but shut off before I can get it checked. Any ideas? Besides the in between 2nd and 3rd it drives pretty normal.