I drove my Kalahari today with the 620-112 fan blade and honestly it seems to do a better job at keeping the D2 cooler at slower speeds. Highway speeds appear to be identical temps, but at slower speeds it appears to do a better job vs the OEM fan blade.

I am retiring my 99's OEM fan blade today for another 620-112. I am running the Auto Zone Severe Duty Fan Clutch for the D2 and the 620-112 fan blade and OEM Grey 180F Thermostats on both my D2's.

 

Just bought the new 620-112 fan blade and mounted it up to a new fan clutch #922790 autozone parts.

will give it a try today. Turning the 36mm nut by hand on the new fan clutch def has more resistance then my old fan clutch.