Update on the car: After driving it a month or two, it developed a unsafe "shimmy" or weird steering shift in the steering when making a hard left at speed. I did some online research and identified a few possible causes. Like usual, I didn't take it to a professional and tried to fix it myself. I thought it was probably related to something I'd replaced over the winter. Did I mention I've not a very good mechanic? But I am persistent. Anyway . . .
So, I guessed it was the subframe mounts, as the car had 240k miles and the visible sides of the mounts looked bad. When the car was up on jackstands nothing felt loose, but of course I couldn't recreate the side-loads experienced on 45-mph sweepers. So I ordered a set of four subframe mounts, watched a couple youtube videos (there aren't many for this repair on first gen w-bodys) and got to work.
First, I supported the engine with a jack and a block of wood and cracked loose the four mounting bolts for the subframe mounts. But I had to use a breaker bar to break loose the rear two mounts, and in doing so I broke the weld on the cage holding the hidden nut that is trapped inside two layers of the unibody by the drivers footwell. I did NOT realize this at the time.
I spent a few hours removing the rusted, disintegrated remains of the original mounts. Initially I just used a hammer and chisel to remove most of the metal and rubber. But the metal parts of the mounts were wedged into the subframe and I couldn't pry them out. After awkwardly fighting it for hours, laying on my back with limited clearance, I ended up using my angle grinder and cutting at the stuck metal pieces. Finally I got it all removed, put the new pieces in place and tried to reassemble them. I couldn't get the parts to compress together, I fought it a while before realizing I hadn't removed all of the metal from the old mount, I thought it was metal from the subframe (I'm an idiot). I tried again to compress the mounts in place but I realized that the nut was spinning and I couldn't get to it to hold it in place! I was many many hours into the project at this point, spread out over weeks of time (vacations and other projects like my 1991 speedboat kept interrupting ) so I dejectedly gave up for a few weeks and left the car in the garage. Eventually I found a thread somewhere here describing how a guy had to cut through the floor to get to the nut. So, without knowing really what I was doing I cut through the carpet and insulation, cut and pried back a few-inch-square piece of floorboard (wow it was thin metal! I've never cut a floorboard before, I just assumed it would be thicker metal), and saw the busted cage around the nut. (see pic of floorboard hole, with broken nut cage removed) Even though the passenger side cage hadn't broken, I still cut through the floor on that side just to see for myself, I figured what the heck I'm already a bajillion hours into this project.
It gets worse. (Did I mention I can make an easy project into a nightmare?). Since I still couldn't get the two subframe mount halves to compress together, I found out from a Youtube video that I needed a longer bolt. But the longer bolts I bought weren't threaded all the way like the bolts that came with the mounts, and when I finally got everything back together (yay?) I didn't realize that I had just tightened the nut down to the end of the threads and it wasn't compressing the rubber mount fully. So I drove it for a few days, but the steering was even worse because the whole subframe was shifting around. I didn't realize why and thought that I'd screwed up the steering rack when I lowered the subframe. Back in the garage it went. Also I didn't realize that when you replace subframe mounts then the alignment gets screwed up so my steering was off center even worse. And with the variable assist steering on my Oldsmobile it feels weird driving with the wheel a few degrees off because the progressive assist doesn't match the on-center steering.
Anyway . . . I eventually realized that maybe I should check if the subframe was tightened properly. When I checked, I could tell the bolts didn't feel tight (because the rubber had compressed more) so I tried to tighten them, couldn't (because the nut was at the end of the threads), and then FINALLY realized what was up, added more washers to allow the bolt to draw up the subframe mounts properly, adjusted my tie-rods again to center the steering wheel, and now four months later it's fixed!
I've driven for a couple hundred miles and it's driving better than it has in years. I need to patch up the holes in the floorboards, currently I just bent the metal flaps I cut back into place and loosely covered with the carpet and insulation I cut out. It's all hidden under my floormats for now, but I need to spray primer on the cut metal to slow the rusting and seal it up better for water and fire protection.
Looking back on the project, I can see many places where I wasted time with the wrong tools, misdiagnosed issues, stupid decisions, and other things I didn't put into this already too-long post. I spent 50+ hours of my life, lost a summer of top-down cruising, and saved . . .a few hundred dollars of mechanic charges maybe? A smart mechanic could have done the whole project much more simply, in a couple hours on a lift with the right tools and expertise. I know that doesn't seem like it's worth it, but it's the principal of fixing it all myself and keeping the car forever.
Anyway, that's my story of the summer of 2019 with my vert, on my back in the garage instead of out in the sunshine. Oh well, she's back on daily driver duty, just in time for the fall rainy season. I wonder what will break next. . .