RE: Bouncing Speedo
Most likely the cable.  I also encountered a problem at the wheel (assuming
2wd) where the square end of the cable comes through the grease cap and
terminates.  The square end was going round, and since it was spinning
sometimes it had rounded out the square hole in the cap.  Solution: new
cable, new (used) cap.
BTW, depending on the year of you Vanagon you may have a two piece cable or
a one piece.  If you have an OXS light on the dash you probably have the two
piece.  If a later model and no OXS light then the one piece, don't remember
the years but I know that '90 and '91 are one piece, I think from '88 on.