kybaseball

Ok in my sons 2005 F150 crew cab we had the transmission rebuilt. The truck seems to be shift hard between first and second. took it back to the guy that did the work and he said that the alternator may be the problem. when you have the AC running it shifts hard between the 2 gears. If you don't have the AC on it doesn't do this. It didn't do this before we took it in the get rebuilt. Could somebody help or may have experienced this and help me with this. Thanks