Transmission does not shift into overdrive

Well, to start out, I had my engine rebuilt at a shop. After that was done, on my test drive, we noticed that the car would not go into overdrive. It had been sitting up for about ten months and before that I had no problem with the transmission. At about 60 miles per hour, the rpm would run at about 3,000. My mechanic who rebuilt the engine couldn't figure why. So I took it to a transmission shop. They told me that there was nothing wrong with my transmission. In fact he told me that it gave a code saying that the cam was out of line. I went back to my first mechanic and he said it was checked and the timing was good. So after that, I took it to a Dodge dealer and had them do transmission diagnostic checks. They came back and told me that I needed another transmission. I figured that if anybody knew, they would. So, I got a cheap one that was certified and checked. Had it put in and having the same problem. So after being mislead by the dealership, I'm lost at what to do next. Please help. You see I've put a lot of money into this. I actually Google it and it lead me to your site.