Drifterpilot,
When the lower shroud is installed there is a screw that must be installed near the middle to keep the shroud from making contact with the fan clutch fan blades. This might be why you have a hole at the bottom. There was a service bulletin that went out to Workhorse dealers to correct this issue on the RV's with the 8.1L engine. The black plastic shroud comes in two pieces and it is important to make sure that it is fastened and sealed so that there is no movement and so that the fan can draw the most amount of air through the radiator.