had the same problem with my 87 300D. had my third replacement. the first is due to a missing lockwasher. the second is due to a worn out pulley (the inner part of the pulley detached from the rest of the pulley leaving the inner part still attached to the shaft and the other part freely rolling with the fanbelt) about the third replacement... i was running quite fast (about 160 kph, quite fast in the philippines) and suddenly the screw of the pulley loosened. i dont know why?!! at the repair shop, we opt to use an electric screw driver to fix the screw in place. but still, there's this peculiar noise from the alternator. I dont know if we have the correct sequence for the pulley, fan, washers, etc. can anyone provide the correct sequence? and also, we are not quite sure if the lock (the tiny metal) is the culprit.