Steve M. asks about a trip odo that doesn't work while the main odo does.
The Vgon speedometer is not all that hard to mess with, since it's not
built into a tin can like some.  The trip odo has a lever arrangement that
takes it out of mesh with the main one while the trip odo gets reset.  I
would say take a look, you might get lucky and find something fixable.  You
could perhaps get the trip odo digits to match the main, even if you 
couldn't get the reset mechanism going again.
B.
Wm Kennedy
kennedy@admin.njit.edu