Hello I have a 09 yukon slt that I got new in 09 , About 6 mons. into the truck I started to notice the idle racing up while I was at a stop light and the truck felt like it wanted to lung foreward . Took it in for service about 8 times before they finally said it was fixed but now as I'm slowing down I can hear and feel the transmission downshifting .....Any ideas???,,,This has been ever since they claim problem was solved...