Alright everyone, really need good news here...
My car has developed a rather subtle shake at around 45MPH. The wheel doesn't jerk back and forth like poor alignment, bent wheel or poorly balanced tire it just kind of gently vibrates. Given the mechanical issues it's had I haven't had it much above 60 for a while but it doesn't seem to get any worse between 45 and 60.
Here's my thought... my right-hand carrier bracket/motor mount bracket is snapped (I believe I've mentioned this elsewhere). Sound like a probable cause? I've noted that the shifter moves about a good bit going from accell to overrun and otherwise. What disturbs me most is that I noticed it shaking subtly when the car began to vibrate. That bracket being busted would certainly be my top suspect given that it holds the half-shaft and is also a stressed member of the rear motor mount assembly.
Obviously it needs to be fixed ASAP and it will be but does anyone reckon it's a big enough issue to warrant pulling the car off the road immediately? I don't have odd clunks, clicks, groans or anything, just the light vibration.