it won't shift when climbing a hill,at times will not exceed

After replacing the engine at 52,342 miles and it was not covered under warranty because it was past the number of years, the car now has a transmission problem. As soon as I picked the car up from the dealership it struggled to climb the ramp and allow me to safely enter traffic. It almost seemed like the car wasn't getting air. The RPM revs to 5 and it feels like it's just not shifting into the highest gear.Ford claims they took this car on a 30 mile test drive after replacing the engine, How is it nobody noticed the AC was not working (that they supposedly fixed after they damaged it ) and the car could not go over 60MPH in NJ in August when parkway speeds are 65 MPH and if you don't do 70 you get run over. No engine light comes on. Car drives fine around town but can not make it up steep inclines and I live in VT. I took it to a transmission shop they could not find anything wrong and it shows no symptoms when they read the computer. I have been told this is the torque converter and 2K to fix. I have been told it's the transmission and it's 7K to fix. I have been told if it's the torque converter than the transmission is shot too..... help