Izicc,
The area you circled was where my leak showed up. Started small, but got bigger to the point where there would be a good pint on the floor each morning due to the crack getting bigger. The oil seemed like it was coming from the seal (see attached, part 050 on the diagram of page 86). Even the dealer thought it was just the seal, and in fact replaced it 3 times before giving up and sending it home.
It took some time to get really bad, but eventually it did. Some really heavy lifting help to speed the process

.
But as you will see by looking at the pictures, it was definately a cracked casting. I wasn't sure where the problem was when I got ready to tear it apart, so I ordered all the bearings, seals, and the bevel gear casting (of course it turned out to be the drive gear casting instead..

)
Picture 1 is one end of the crack.
Picture 2 is the other end (kinda hard to see in this picture, but it runs all the way down to the left side of the picture following the curve of the casting).
Picture 3 & 4 are the inside of the casting. If you look just left and just right of the center of the pictures you can see to black spots where the casting had chipped away. Zoom in on those spots and you can see and follow the crack from one side of the picture to the other. It was hard to see initially, but the black spots clued me in on where the crack was on the inside.
The last picture is to give some perspective on where the crack is on the casting. In fact if you look to the left side you can get a better view of what picture 2 was trying to show.
The other attachment is a few pages of the parts manual.. The casting cost about $130 from Coleman Equipment in KS, so just hope it is only the seal that needs replaced.