[Early_S_Man]

Markus,

My take on the gradual improvement ...

There were microscopic bearing and gear wear products that had worked into the complex synchronizer mechanism, and were causing the grinding you noticed. After the change to SWEPCO, the superior additive package slowly worked the wear particles loose [detergent action] and they began to be carried around in suspension in the gear oil, and finally were collected on the drain plug magnet as 'fur or fuzz' we find when we change the oil!