While replacing the rack and pinion on my 2008 Uplander I attempted to loosen the rear subframe bolts to lower it at get more access. I was able to loosen the passenger one just fine but the driver side was tight and I believe I have spun the captive nut in its cage. I now can't loosen or tighten it back up... or just spinns.

There is no obvious way to cut a window into the frame for access because it is at a sort of T section of the frame. I'm thinking it may be accessible through the interior floor (like the Traverse). But before I start doing exploratory surgery and cut holes in my floor or frame I figured I would ask here to see if anyone has been down this road before and what the best solution is.

 

For thoes looking for a solution to this in the future... hope it helps.

I was able to access the captive nut by going through the floor. After pulling up the carpet and removing the e-brake cable grommet I was able to see through to the outboard subframe bracket nut. Using this as a reference I eyeballed the fwd/aft location and measured 6" inboard of the bracket nut to where the mount nut should be and started drilling. It is pretty much just where the floor pan starts to bend upwards.

There are three layers... first is a thin layer of sheet metal making up the floor pan... second is thicker and what appears to be the top of a beam... third was the bottom of the beam but it already had a slot in it that just needed to be opened up to fit a 15/16" socket (its probably metric but 15"16 fit snug).

This seemed to work better than any solution I could think up to access the nut from underneath.