Morris,
Ok, thought that it looked like a large hole for a vent. There is a small hole that has a plastic plug in it directly over the differential
oil fill hole towards the top of the cover, I imagine that is where the vent is supposed to be. Not sure why it is plugged. I do not see any other openings on the differential cover.
I can easily make another cover to block that return hole for the differential cooler, or decide to plumb in a differential cooler. Not sure that I will need one as I do not plan on running any endurance races right now.
the weather has turned cold again, so I will wait until it gets warmer before taking the rear cover off and seeing what is there. Will take your advice concerning how the hose that runs to the catch can is connected.
Thanks for the advice, greatly appreciated.
Jim