I had the same symptoms and did the same things, and it
turned out to be the tranny.  Do you have between 80,000 and
120,000 miles on it?

One other thing to check is to make sure your rear brake
shoes are not hanging up due to mal-adjustment/alignment.
steve

John Mates wrote:

> Regarding my plea for comments regarding my 86 syncro
> which vibrates strongly at certain RPMs under load...
>
> A reader pointed out that I didn't mention what
> effect NO driveline had on my syncro.  The vibrations
> were reduced in strength but were still easily felt,
> so I figured the driveline was amplifying the vibration
> that was already there.
>
> Also, I didn't mention that, along with everything else
> I mentioned, I put new OEM shocks on the back.
>
> John
>
> \ o /  __o        __|    \/
>   |     /|   __\o    \o   |
>  / \   |\  /)  |     ( \ /o\
>
>  John Mates, Intel Corp.
>
>  JFT
>  5200 NE Elam Young Parkway
>  Hillsboro, OR 97124-6497
>
>  jmates@ichips.intel.com
>  (503) 264-8023
>  #include <std.disclaimer>