Having a SpeedHut diff temp gauge installed. Watching the temps today. It's 40F outside. Diff temp went to 200F after about 20 miles and stabilize. Turned on the pump and watched the temps drop. Turned the fan on and the temps dropped even quicker.
At an idle. You can hear the pump and fan. But soon as you get going. You don't hear them. My FI exhaust covers up their noise.
The OS Giken diff is a bit clunky in operation at low speed. You know it's working.