i was having the same problems and more ,I installed a shift pro kit,a new shift star,a new shift shaft with a new spring on it, and also changed the adjustment bolt for the shift shaft.that bitch shifts smooth now.on mine the spring on the shift shaft was worn and also the egg shape was worn out on the adjustment bolt, so I could not get a good centered adjustment on the shift star. i would not tear into the tranny until you rule out the little things
-Mark-