ac not cooling enough 2002 Durango

My 2002 with rear ac will only cool to 63 degrees in front and 59 in the back at idle with ambient temp above 90 degrees. It will cool to 58 degrees in front and 48 degrees in back running down road at 60 mph. I have replaced electric cooling fan, compressor, both expansion valves, and radiator and thermostat. I have 2.44 lbs of R134 in it. Does anyone know how to get it colder? AC has never cooled well, even when new. Pressures will equalize after shut down. At 90+ degrees, best cooling pressures for vent temps described
above occurs at 50 psi low and 200 high.

48 degrees in the back sounds pretty normal. I wonder if you have a blend door issue in the front? For giggles what does the temp in front do if you pinch off the hoses to the heater core?

these model year durango's are known for junk ac temperatures, I think they have under-engineered the system....Though speaking with other tech's in the shop, some have said that they found the ac to blow a little colder after they vacuumed the system found about 1 hr...

You can put some kind of water shut off valve in the heater hose supply to the core. There is no water valve in this system so hot water is always circulating through the heater core.

Will the water circulate good enough if I block the heater core off?

Never had a problem with the one's I did.

OK, just didn't want to create to much back pressure or anything. Just to make sure I understand you right, I don't have to splice the supply hose and the return hose together? I could just put a ball valve or something on that one hose?

That how I did it. And yes this system was definately under engineered.

Well, i tried it but it didn't help. Any other suggestions?