OK...an update. I've been casually looking into the
previous suggestion to check/replace the rubber cap that
covers the vacum adjustement mechanism. Although
my cap was "cracked" every mechanic I talked to said:
"its just a cover and doesn't affect the transmission".

Well two weeks ago I subcribed to alldata.com and checked
out the tech bullitens and found one that talked specifcally
about this rubber cap and the affect it has on shifting.
I had it changed last week and what a difference!

This did not fix my 2-1 shift thump, but guess what, there
is a tech bulliten on that too!

Just though I would share this info.

Thanks