Transsmission slips and My A/C only gets colder when at idle.

My A/C was working fine until recently. It blows warmer air when I'm driving but gets colder at idle. Rear A/C is colder than front.... Other issue I'm having is the transmission. When the truck is cold I have to put it immediately in gear and make sure I keep moving until tranny warms up. If I get stuck at a light while cold it will not engage into drive or reverse