Shaking steering problem

[Eddie <axr11@po.cwru.edu>]

I have a 99 GLX (A3) with 42,000 miles. From about 55-70mph, my steering
shakes pretty badly. I went in and had my wheels balanced (they were
apparently quite unbalanced...), and an alignment done. (The wheel doesn't
pull in any direction, though) But the problem has not subsided at all. The
mechanic told me that something might be going wrong in the front end, but
after checking, he said that everything was still nice and tight, and he
doesn't see anything wrong, and to bring the car back if and when it gets
wrose. I've been having this problem since late october, and it is quite
annoying, esp. when braking through those speeds, and it also feels unsafe.
And it hasn't gotten any worse or better. Anyone have any ideas as to what
it could be? Something wrong in the steering mechanism?

Thanks in advance...