Oh boy, I need to do some more digging. On  the oil, they did not want anything thinner than 10W -30. Now in the same token I had a customer when I did the truck type hydraulics  for my other employer and they exported quite a few trucks they went to ATF and reduced there problems  for warrenty claims by over half. Chris: that tube was added to the early units that had the smaller oil capacity. The key thing is the return oil should return the oil away from the pump pick up tube. Remember the difusser package for the 55 series? Same idea. More on that later as well.