Actually, what you described sounds totally normal to me. Normal in that if the VX has not had regular, COMPLETE tranny services done every 30k then you will start to here the clunk.
When you come to a stop, the VX will downshift and you will hear/feel a clunk. When I bought my VX, shifting up from 2nd to 3rd was harsch, even violent at times. I did a complete tranny service at that time, and kept up with it, and have not had any more harsch clunking at all.
I would say, since you just bought this VX and most likely do not know when or if the tranny has ever been properly serviced, its time to make friends with some local VX owners and get your tranny job done. It will cost you under $100 to do it yourself, and a Saturday of work, but it will make your VX that much healthier, and the clunking will be much, much better.
That's just my 2 cents...
Bart