Is it a nut, or a allen head, like the differential in the rear?

I made my own wrench for the diff (not that I need it, but seems most euro cars are the same, and we actually do need it for my brothers 924. Basically welded a 19mm (i think) bolt to a steel rod. Its a very large hex wrench that really only has one purpose.

 

idk yet...look in your cd repair manual it looks like a nut but not sure...i'll put it on a lift this sunday hopefully