Thanks all. Yes, the engine is turned up with torque plate 8. I have replaced the TC with a stronger after market. I have installed the BD Performance pressure modifier that increases pressure at low RPM. I am the only driver and watch very carefully for slippage when I tow, and slippage very seldom occurs (only when cruise control makes the Cummins get out of hand in steep slopes... I then make a habit of deactivating it to prevent the risk of slippage). The lubricant is perfectly clean after 50k highway miles since new TC and oil. I was just curious about the clutch mechanism, since it's impossible to peek inside. It makes sense that clutch wear material be carried in the oil instead of build up inside the TC.
To the question about miles, 220k. Transmission works like new, never abused, replaced original TC with billet TC at 185k. I also have the BD Performance pressure control kit
Click. Next job is a Transgo TFOD Diesel VB kit installation.