Just wondering if anyone has had this problem with one of their vehicles or know what it could be. When driving my truck around town I have no problem, but once I get over 80 kms an hour, my check engine light comes on and my truck starts to shift really really hard. I have taken it to a chevy dealership to have them check it out, they said the only code in it is my 02 sensors. They supposidly took it for a test drive and could not duplicate the problem, however as soon as I picked it up and got about 15 mins out of town it did it again. When driving the truck in Drive it seems to be fine, however in over drive it does it everytime, if I stop and unhook the battery for less than 5 minutes, and hook it back up and drive it again, it is fine until I go over 80kms again. . . . . Please help, I have had this problem with my truck for over a year now, and it is very frustrated, especially that everyone I have asked to look at it, doesn't know. . .