Differential bolts
 

How do the hex bolts on the front of a 2nd gen differential for a W126 hold it in place against the rear subframe?
I loosened them but I can't seem to take them off or tighten them back on. When I put my hand above the subframe where they are suppose to have some sort of a nut all I feel is a rubber disk that's spinning whenever I tun a the bolts. I am stuck!
I can't lower the diff like I first intended and I can't tighten it in place now that I changed my mind.
Any help will be appreciated.

There should be a 17mm nut on top of the washer stack. It's a bear to get a tool on and hold. A stubby 17mm wrench is my first choice.

I couldn't feel a nut in there, just s rubber disk that spins when I turn the bolt.