This past Sunday my wife and I had just come back from vacation so I had a few hours to work on the tbird again while she and the kiddo took a nap -- my vacation
While underneath my car, I found that amazingly enough after 3 years of hard abuse, my subframe bolts (the one with the funny ETORX heads on them) were loose. How loose? Well, 2 on the passenger side and 3 on the drivers side were looser enough you could visible see the threads?!
Just to keep me sane, I checked with the frame shop to see if this loosening was part of some kind of frame straightening procedure. It's not
The most likely answer is that when I first converted this car to a V8 three years ago, I had the smart idea that I needed a 7qt oilpan and this this required me to loosen my subframe bolts (and break 20 years of crud/whatever that had kept those bolts in place since the car left the factory). Over the past three years these bolts loosened themselves out. Scary.
Bottom Line: if you've ever loosened your subframe bolts in the past (or even if you haven't), do yourself a favor next time you are underneath the car and CHECK YOUR BOLTS.
PS. When I asked my autobody guy about this, he said that the last lemons car he fixed had used wheel spacers and they had apparently lost 3 out of 4 of the bolts holding the spacer onto the hub. Yeah, that would have sucked.