Oh brother, does this ever sound familiar
I would say to check your rear control arm bushings just for good measure, but the problem slowly came back on my car even after the rear control arm bushings were replaced.
I did everything listed here as a possible solution (except replacing the bellhousing), and a whole lot more. Although I am very reluctant to declare that my problem is fixed, it appears that it is. I haven't driven it enough since the last repair attempt was completed, as there have been a few other issues that I have been working on.
Even if it is indeed fixed, the bad news is that I am never going to know a definitive cause for the problem....it's a long story
So, although I wish I could point to some specific thing to tell you to check.....I can't