Every time I had a bad thunking noise on the front end of my van that
mystified early diagnositc attempts the noise turned out to be a bad ball
joints. This happened to me 3 times, two on the '72 bus, and once on my '90
Syncro Westfalia. Each time it never occurred to me that this could be the
cause, and each time I swore that if I had a thunking sound up there again I
would think of the ball joint first. 

Derek Drew