Ever wonder what a magnetic drain plug on a transmission collects over 40 years? This was my plug from the replacement transmission. The magnet is designed to remove metal filings from the gear oil and keep them away from the gears, thereby reducing wear. To my knowledge, it was the first time the plug was ever pulled and the gear oil changed. The original transmission (the one that broke) didn’t have a magnetic drain plug and I could see metal filings floating when the gear oil was placed in sunlight.