Does the noise occur with the A/C engaged or without. With the A/C OFF, the clutch on the compressor freewheels on its own bearing. If it is noisy with the A/C on and it's not the belt slapping, then the compressor bearings or internal other parts are shot. If the compressor is gone, DON'T use the A/C at all. The disintergration of anything internal on the compressor WILL contaminate the whole system. If you replace the compressor, replace the receiver drier also.

__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.