All of the cooling fans I have heard on vanagons were very quiet at low speed.
It is only at the higher speeds are they a problem. Do you know if your
thermoswitch is working right to make the fan go on at low speed or is it going
right to high?

Later vanagons even have 3 speeds, the highest I refer to as melt down speed and
its real loud.
Check out the system before you chaulk it up to "they all do that"