[Vjlaw72]

I have a 4l60e and I did a transmission flush on it and two weeks later it started the problem that I mentioned. It wont shift out of first unless i let off the gas then it shifts fine into second then third but overdrive dosent work either. Reverse works fine. I replaced the speed sensor,tps sensor and some of the shift solenoids and pan gasket and filter. There are no codes showing and I have 327000 miles on it. What could be the problem.