rampart03

I'm trying to remove a center differential from a n 87 4000CS Quattro while the transmission is in the car. I got all the bolts loose and removed the plug that has has the star shaped turning spline as shown on page 34.54 of the Bentley Manual. That page refers to a hollow bolt to remove besides the end plug with the tapered star spline. My 84 Quattro has a hex head bolt under the plug. What does the later differentials have. Is is a hex hollow bolt, or a standard octagonal bolt with a hollow center. I can't see in the hole to determine. I tried a hex socket, but it didn't seem to grab very well, kind of like grabbing on the hollow star shaped splines. Does anyone know how to remove this "hollow bolt", and if so what socket should I use.

Thanks in advance

Ramp