If your '85 has the original Sanden/Sankyo ac compressor it will be noiser
if the refrigerant amount is low.  Or of course if it is wearing out.
Also carefully check comp. v-belt & pulleys on crank & comp. Any uneven
wear can cause vibration & noise.  Many "cheapo" belts are uneven width
all the way round & will cause a vibration at certain rpm.  Belts from
NAPA/Gates are more money but usually better quality & run quieter.