Just and update. Per advise from another forum, I added a tube of Dr. Tranny 19610 Instant Shudder Fixx Friction Modifier. It eliminated the shudder completely and almost instantly. I don't know what the stuff does, but everything is operating like brand new now.

 

it does just what the title says: the crappy fluid in the trans had the wrong friction co-efficients. Your lucky running that walmart fluid didn't damage the transmission.