ok, i'll be serious, too.  at one point i had a thunking problem too. 
how's your clutch?  i tightened mine a little and fixed the 'thunk'

>  > 
> >my shifter used to not feeel to good too...IT FIXED ITSELF !!!!!  the
> >procedure was as follows:
> >
> >talk really nicely [read 'curse violently'] to your reverse gear while
> >pushing your van backwards.  go out to drive it one day and discover that
> >not only has reverse returned from the dead, but _everything_felt good.
> >
> >simple huh?
> 
> So that's the problem... I'm using wrong procedures and tools! Trashcan the
> Craftsman stuff, parts, and moly grease... turn to the Karma section in
> St. Muir! Practical, makes sense, feels right, and it's free! and worth
> every penny of it, for sure!
> 
> Seriously, Bob, my '71 tranny seems fine once I get it into gear-- no popping
> out, grinding, whining, etc. But getting it in can be an interesting
> exercise. Is the gear after first going to be second, or reverse (ouch!)?
> And after slowing for a corner, I coast blithely through the intersection
> with cars piling up behind me, as I try for the sixth, then seventh, then
> eighth, etc. time to get it into second. Finally (when I make it an offer it
> can't refuse) it goes in with a loud CLUNK, and away we go.
> 
> Looking at the little cagelike connector between the shifter and the
> tranny nosecone, it looks shiny and new. But several folks have suggested
> replacing a bushing that exists somewhere in that general vicinity, and one
> has suggested looking for worn surfaces on the steel shift fork inside the
> tranny nosecone. Sounds good!
> 
> Thanx for the info so far, ladies and gents. This is a great list-- keep
> up the great work!
>