Well I don't know what the problem is because I am really not keen on trannys, but I definately do have a problem. I have a 4T65e w/ about 88k miles on it. And lastnight on my way home, it felt different. I get out on the highway, start accelerating, it hits 3rd and just keeps climbing. Passes 6k(I have a DHP) and I am not even WOT(about 70%), and keeps going all the way to 6400 and hits the rev limiter(or valve float one of the two), and keeps bouncing, I had to let off the gas to 0% to get it to shift. Did this all the way home, I would slightly accelerate to pass, it would downshift as if I was hitting the throttle hard, stay in 3rd and wouldnt go into 4th without letting off the gas. I cycle through the gears manually and find that it won't downshift into 1st either. Anyone have any suggestions? Is a rebuild a remedy?? I can swap cams, heads, rockers, you name it engine wise. But when it comes to trannys I dont know my ass from a hole in the ground. HELP!!