DutchDoofus

Over here in Europe the following product, which is added to ATF, yields very good results in older tranny's which sometimes shift a bit harsh/yerky.
This additive make the shifting remarkably smoother in older transmissions.

"FORTÉ AUTOMATIC TRANSMISSION TREATMENT"
http://www.forteuk.co.uk/Automatic_transmission.htm

Use two tubes a week prior to an ATF change to loosen gum and goo from the inside.
(just open the filler-plug and squeeze in the tube, then seal the tranny like normal.
You will find black "thick tooth-paste like crap" flowing out with the old ATF during the atf-change job a week later.

Then, while filling the tranny back up with ATF, use one tube if the customer experienced light shift-jolts and two tubes for harder shifts.

This stuff will make a tranny live longer. I use it before and during every ATF change (every 35.000 miles) and my tranny is still in acceptable condition after 190.000 miles.

On high performance cars like the RS6 (C5) cars over here, two tubes along with fresh ATF make a positive difference in shifting (smoother).
My A8 likes this stuff too (and his boss also :-)