This happened to me on my 96.
Really a pain on the highway. Hit a cetain speed/RPM and the shifter buzzes.
My dealer came out with me on a test drive and I was able to demonstrate the buzz (I was lucky that day).
Under waranty they replaced the entire stick assembly. Even got a new shifter knob that was leather wrapped that came on the new stick.
Never had problems since. I am sorry that I can't go into further details on what was wrong, it was 5 years ago.
You know how they do it, just replace everything instead of pin pointing the problem.
