it is low on freon takes 3.5 lbs and every chevy in that system has the same problem the front a/c tube has an orofice and the rear does not it's a design flaw so it takes more pressure in the system to flow the freon. I had a radiator shop put a orofice tube from another a/c system in the line and both front and rear a/c's are throwing ice cubes half to run a/c on medium blower setting. Note retired chevy tech.