When we accelerate the a/c makes a horrible racket. when a/c is off- no noise. the belt broke yesterday. replaced belt so we have a/c, but still makes that loud sound when we take off or are at high speeds. what do we need to replace? thanks!

More than likely the A/C compressor has failed and the clutch is doing it's job isolating the compressor from the belt when the A/C is off. Leave the A/C off and get your dealer to quote you on flushing the entire A/C system and replacing the dryer, the valves and the compressor/clutch assembly. A failing compressor often spews little chips of metal into the A/C system contaminating the dryer and the valves in the process. A really bad compressor failure may even clog the evaporator. It will NOT be cheap but it will fix the problem. Avoid the cheap A/C recharging kits found at Walmart and "auto parts" stores. IF they appear to work at all it is temporary and they contaminate the system even more; often requiring complete system replacement by contaminating the lubricating oil in the compressor.

Sounds like the clutch assembly for your A/C unit is toast!! thats why the belt broke, Hopefully its not the whole unit seized,, that gets expensive !!