tuaudi

Would also sure like to learn if low fluid pressure is the culprit ... I have precisely the same problem (a jerk/clunk during downshift in coast down between 2nd and 1st gears) on my 2000 A8, 44K miles, and the problem was unaffected by a recent transmission fluid & filter replacement (trans was leaking, and fluid low, neither of which was identified/corrected curing an Audi "certification" inspection by the Audi dealor frow ehich I recently purchased the car).
I have also had one incidence where under hard acceleration from a low speed (about 20 mph, transmission probably in 2nd) the trans simply disengaged (engine speed spiked), and the trans did not re-engage until I fully released the throttle.

audilvr

My neighbor works for Accurate, and Accurate is a supplier of parts to trans shops-- essentially a wholesaler. THey get a lot of business on the A8 trans.

If you rebuild, get a valve body replacement and recode to .00011