Front A/c Warm Rear Is Cold

I have a 99 suburban with rear air and the rear is real cold, but front is warmer (Quite noticeably warmer yet still cooler than outside). The back will freeze my baby while i sweat up front. The A/C pressure is good, the vent door to heater core is closed, the A/C evaporator (coil) is clean. What can it be. What does the accumulator do? Is it possible my evaporator is partially clogged? Please help. I know you know a lot Yukon, so all help is appreciated.

Thanks
Sidman

you've probrably solved this problem since its been two months but, was it your front orphice tube? I had the same problem in my 95.