our old UniMoG transmission, the gearshift rattled terribly, it nearly
drove you nuts on the highway. Our solution at the time was a
bungee cord hooked to the gearshift & the passenger seat. It
didn't put much force on the gearshift, just enough to keep it from
vibrating. The bungee could be removed easily when using the
lower gears exclusively, so that it didn't piss off the driver to have
a tethered gearshift.
replacing our transmission, we discovered that there was supposed to
be an o-ring in a groove on the gearshift. Looking closely at
the old one, sure enough, there was a well squished o-ring, much too
flat to do the job. The o-ring on the new transmission was
actually a little big & torn while being put into place, but it
did keep the gearshift from rattling for quite some time.
fishing through our drawer of leftover Volkswagen gaskets (doesn't
everyone have a billion leftover gaskets for their type I engine?
Every time you want valve cover gaskets, you buy the whole gasket set
because it is cheap) we came across an o-ring just the right size!
If you want to get picky, it is a D-ring, with the flat part of
the D facing toward the center of the circle, but it fits the
gearshift perfectly. It is the sealing ring for the distributor,
not something you need all that many of, they don't get replaced
often. Now we can keep our gearshift from rattling & carry a
spare o-ring without spending any extra money.